Drinking water
2015
Public water supplies in the
Western region of England
July 2016
A report by the Chief Inspector of Drinking Water
Western region
Drinking water 2015
Western region of England
1
Drinking water 2015
P ub l is he d b y
Dri nk i ng W ater Ins p ec tor at e
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17 Sm it h S qu ar e
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Co p yr i gh t i n th e t yp o g r ap h ic a l ar r an g em ent an d d es ig n res ts wi t h t he Cr o wn .
T his p ub l ic at i on ( ex c lu d in g t he lo g o) m a y b e rep ro d uc e d f r ee of c h a rge in an y
f orm at or m ed i um pr o v i de d t ha t i t is r e pr od uc ed ac c ur at e l y a n d no t us e d i n a
m is le a di n g c o nt ex t . T h e m at er ia l m us t b e ac k no wl e d ge d as Cr o wn c op yr i g ht wi th
th e t it l e a nd s o ur c e of th e p ub l ic at i on s pec if i ed .
2
Western region
Contents
Chapt er 1:
Summar y
4
Chapt er 2:
W ater supply arrang ements
10
Chapt er 3:
Drinking water qualit y test ing
14
Chapt er 4:
Drinking water qualit y results
17
4.1 Microbiological qualit y
17
4.2 Chem ical qualit y
28
Chapt er 5:
Drinking water qualit y events
47
Chapt er 6:
Technical audit activit y
58
Annex 1:
Further sources of inf ormation
65
Annex 2:
Guidance and resear ch published by DW I
66
Annex 3:
Drinking water qualit y events in the region
68
Annex 4:
Planned drinking wat er qualit y improvements
84
Annex 5:
Compet ition in the water industr y
87
Annex 6:
W ater company indices
89
Annex 7:
Glossar y and descri ption of standards
92
Drinking water 2015 is the annual report of the Drinking Water Inspectorate and
c o mp r i s e s r e p o r t s c o v e r i n g p u b l i c a n d p r i v a t e w a t e r s u p p l i e s .
Public supplies – This part describes drinking water quality in the Western region. The
I n s p e c t o r a t e a l s o p u b l i s h e s a s e r i e s o f c o mp a n i o n r e p o r t s f o r o t h e r r e g i o n s o f E n g l a n d
(Central and Eastern, Northern, and London and South East regions) and a separate
report for Wales.
P r i v a t e s u p p l i e s – A s u m ma r y o f i n f o r ma t i o n o n p r i v a t e w a t e r s u p p l i e s i s r e p o r t e d f o r
England and Wales.
A l l p a r t s a r e a v a i l a b l e o n t h e I n s p e c t o r a t e ’s w e b s i t e w w w . d w i . d e f r a . g o v . u k
3
Drinking water 2015
Chapter 1: Summary
Chapt er 1:

Provides a summar y of the report f or the W estern region.

Puts drinking water qualit y in the region into context nat ionally.
Drinking Water 2015 is the annual publication of the Chief Inspector of
Drinking W ater f or England and W ales. It is the 26 t h report of the work of
the Inspector ate and presents inf ormation about dr inking wat er qualit y f or
the calendar year of 2015. It is published as a series of seven reports, f ive
of which cover public water supplies and two descr ibe private water
supplies. This report is about public supplies in the W estern region of
England.
Set out in this report are the key f acts about the q ualit y of the public water
supplies in the W estern region, which is ser ved by seven wat er companies
delivering supplies to 4.7 million consumers. The area ser ved by each
water company is shown i n Figure 1 and the organis ation and nature of
water supplies in the W estern region is described in more det ail in Chapter
2. There were no changes in the water supply arrangements in the region
in 2015 compared to 2014. In Apr il, Pennon Group Plc (par ent company f or
South W est W ater) acquired Bournemout h W ater f rom Singapore-based
Sembcorp. The t wo companies continued to report separ ately f or the
remainder of 2015 and so a ppear separately in this report. There were
changes also in the number of private water supplies in the region not if ied
by local author ities t o the Inspect orate with the total increasing f rom
12,890 in 2014 to 13,285 in 2015. Detailed inf ormation about t he
regulation and qualit y of private supplies can be f ound in the separate
report entit led Drinking Water 2015 – Pr ivate Water Supplies in England.
The qualit y of public water supplies in England in 2015 was very high with
only 0.04% of tests failing to meet the European Union ( EU) and nat ional
standards. This com pares f avourably to t he 1.6 % of f ailures recorded in
1991, the f irst year af ter privati sation of the water industr y, when
regulation of drinking water qualit y was f irst introduced. The situat ion in
relat ion to the quality of private water supplies in England remains less
satisf actor y with 4.5% of tests f ailing to meet the EU and nat ional
standards in 2015. However , this f igure compares f avourably t o the 7.5%
of tests that f ailed in 2010, the year when new regulations implement ing
the EU Drinking W ater Directive f or private supplies were introduced.
4
Western region
Figure 1: Water suppl y arrangement s
The results of testing of public supplies in 2015 demonstrated that overall
the qualit y of drinking water in the W estern region was good. The f igure f or
compliance with dr inking water standards was 99.96%, the same as the
regional f igure in 2014, and the same as the industr y average. The
Inspectorat e uses a range of indices to assess the water qualit y
perf ormance of the companies providing public supplies. These indices 1
look in turn at water treatment (process control and disinf ection ind ices),
ser vice reser voir int egrity and net work maintenance. Individual water
company f igures are set out in Annex 6. In 2015, the changes in the
W estern region were an improvement in the f igures f or disinf ection
(99.99%) and net work maintenance (99.91%) . Both f igures show an
improvement on last year and are above t he respective 2015 industr y
averages. The ser vice reser voir integrit y index (99. 94%) is eq ual to last
year and again above the industr y average. The process cont rol index f or
this year ( 99.98%) is slight ly lower than both the regional f igure f or last
year and this year’s industr y average (both 99.99%).
1
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ht tp :/ /d wi . d ef r a. g o v. uk /a b ou t/ a nn u al - re p ort /c a lc u l at i ng - i n d ic es .p df
5
Drinking water 2015
Figure 2 shows how the change in the disinf ection index f or the region in
2015 was mainly attributable to improvem ents made by W essex W ater
where there was a notable reduc tion in the number of f ailures at works f or
colif orms and turbidity . This is a result of a strategic initiative by the
company to manage the risk of those sites (see Chapter 4. 1:
Microbiological quality – Turbidity).
Figure 2: Company performance for the disinfection index
Across the W estern region , in 2015, there were f ewer events aff ecting
water qualit y overall ( 72 compared to 85 in 2014). A notable f eature of
events in the region in 2015 was an incr ease in events report ed due to
public concern, many of which were relat ed to domest ic plum bing causes .
In 2015, in the W estern region ther e was an overall reduct ion in signif icant
events of 33 taking this below the levels seen in 2014 and 2013 of 53 and
41 respectively. A single ser ious event was, however , recorded in
September at Bratton Seymour reser voir where W essex W ater issued a
boil water not ice to 258 properties f ollowing the detect ion of E.coli and
colif orms (see Chapter 5: Drinking water quality events and Annex 3). The
cause of this event was a secon d hole drilled int o the side of an access
hatch intended f or cables which remained unused and unsealed and
through which mice were able to access the inter nal compart ment. The
Inspectorat e visited the site to ensure that the actions taken were
appropr iate. This event illustrates the unmitigated risks contractors may
pose while completing a simple installation which subsequently af f ects
water qualit y. The company , f ollowing this event , reinf orced their n ew
qualit y scheme f or W ater Supply. ‘Think Qualit y, Be W ater Smart’ to
ensure all those who visit and work on their site s are aware of their
responsibilit y towar ds saf e water. This builds upon the successf ul and
similar initiative by Northumbr ian W ater the year bef ore which other
6
Western region
companies m ight f ind usef ul . In March 2015 Bournemouth W ater pleaded
guilt y to f our counts of supplying water unf it f or human consumption and
one count of f ailure t o adequately operat e a treatment process. The case
related to an out break of Cryptosporidiosis in Bournemouth linked to th e
water supply in 2013. The charges were brought under Section 70 of the
W ater Industry Act 1991 and Regulat ion 26 of the W ater Supply (W ater
Qualit y) Regulation s 2000. The company was f ined £20,000 on each of
f our counts of water unf it plus £5,000 f or the count of f ailure t o adequately
operate a treatment process, totalling £85,000 and paid £48, 772 towards
prosecut ion costs and a £120 vict im surcharge.
In 2014, the Inspect orate put in place a P rovisional Enf orcement Order
requiring Br istol W ater to comply with the Inf ormation Direct ion in relat ion
to notif icat ion of events. In March 2015 t his Final Order was put in place
because an audit had shown that the company had not f ully complied with
the provisional Order. The Inspectorate were sat isf ied with t he ac tions of
the company at a subsequent audit and r evoked the Order in August 201 5.
In 2015, t wo events occurred at large treatment works (Frankley works
(Severn Trent W ater) and Franklaw works (U nit ed Ut ilit ies )) which
identif ied issues f or considerat ion by all companies. The f ailure of these
two treatment works highlighted the need f or longer strategic planning to
avoid f ailur e to supply wholesome water t o consumers at all times where
there is no obvious opportunit y to recover . Plans should include
interconnection bet ween works and systems, process redundancy,
operat ion within design limits, technolog y and compet ent staff all brought
together through risk assessment and mit igation. This year, companies
submitted their r isk assessments to the Inspector ate and it is clear that
long-term asset planning f or water qualit y will need to be a priorit y.
The Inspectorate, as part of its risk -based strategy, ident if ied Severn Trent
W ater and United Ut ilit ies as companies where the risk of regulator y
f ailure was consider e d greatest and where a risk reduction pr ogram me to
support improvement through programmes of work was merited. Severn
Trent W ater , who were the f irst company to engage with the tr ansf ormation
programme f ollowing a number of challenging years reported in th e Chief
Inspector ’s reports of 2014 and 2013, agreed an extensive f orward plan f or
improvement cover ing works and ser vice reser voirs. The Inspectorate is
pleased to report that whil e the process is still ongoing, the posit ive
response by the company has sh own benef its in the reduction of risk. The
transf ormation programme f or United Utilities started at the end of the
year. The programme encompasses a much wider range of risks , including
the need to ref ocus company staf f on drinking wat er qualit y and
repositioning the organisation as a ser vice company to meet customer
needs and expectat ions. The Inspector ate reminds companies that
overemphasis on a selected number of end point compliance parameters
7
Drinking water 2015
can result in f ailure t o identif y key risks throughout the s upply of water ,
which consequent ly r esults in f ailure to pr oduce a clean wholesome
supply.
Local authorit ies across England and W ales provided case st udies on the
remediation of f ailing privat e water supplies. T wo examples relat ing to the
W estern region can be f ound in Drinking water 2015 – Pr ivat e water
supplies in England – Chapter 3: Improving private water supplies .
More inf ormation and industr y - wide learning points about these and other
signif icant events can be f ound in Chapter 5 and a summar y of all
signif icant events in the region can be f ound in Annex 3 of the report.
Table 3: Water qual it y events in 201 5
Nat ur e of ev e nt
Ce ntr a l a n d E as t er n
Lo n do n a n d S ou t h E as t
Nor th er n
W es tern
W ales
Indu st r y
Ri sk as s es sm ent cat ego r y ( DW I)
M inor*
Si gnif i ca nt
S er iou s * *
20 1 4
20 1 5
20 1 4
20 1 5
20 1 4
20 1 5
11 9
12 9
59
48
5
4
90
97
53
62
6
2
28
44
48
64
1
3
32
38
53
33
1
13
16
10
18
28 1
32 2
21 8
22 3
12
10
F o u r e ve n t s a f f e c t e d t wo o r m o r e r e g i o n s i n 2 0 1 5 a n d f i v e i n 2 0 1 4 .
* Mi n o r c a t e g o r y n u m b e r s i n c l u d e a l l n o t s i g n i f i c a n t a n d m i n o r e ve n t s .
* * S e r i o u s c a t e g o r y n u m b e r s i n c l u d e a l l s e r i o u s a n d m a j o r e ve n t s .
During 2015, the Inspectorate carried out 88 audits of assets, sampling
arrangements and consumer complaints in England and W ales, 17 of which
were in the W estern region. In addit ion, t he Inspectorate received reports
submitted by the industry which identif ied risks f rom source to tap f or all
supply systems. These detailed reports are currently under review and the
outcomes will be reported in the Inspectorate ’s new quarterly report.
W hen consumers are dissat isf ied with the qualit y of their dr inking water
they may contact their water company. Records of the number s of contacts
received by water companies are sent to the Inspector ate each year. In the
W estern region the total number of consumer contacts to water companies
about the qualit y of drinking water was 2.4 contacts per 1, 000 populat ion,
50% higher than the industr y average of 1.6 contacts per 1,000 population.
If the water company f ails to address the co nsumer ’s water qualit y issue,
the consumer can seek assistance f rom the Inspectorate. In 2015, the
Inspectorat e invest igated 47 consumer complaints of which eight (7 SW T,
1 BRL) were in the W estern region.
Also, during 2015, the Inspector ate handled 297 requests f or advice about
private supplies f rom local aut horit ies acr oss England and W ales and 43 of
these enquiries wer e from the W estern region. Audit f indings and
consumer complaint case examples can be f ound in Chapter 6 and details
8
Western region
of the work of the Inspectorate in relat ion to privat e supplies can be f ound
in the companion report entitled Dr inking water 2015 – Pr ivat e water
supplies in England.
Turning to planned improvements in dr inking water qualit y in the region,
during 2015, the Inspectorate conf irm ed the need f or improvements at
Tamar works (South W est W ater) and Knapp Mill works (Bour nemouth
W ater) to address risks posed by manganese and discolourat ion and
Cryptosporidium respectively.
Companies in the region are committed to complete the planned work
summarised in Annex 4 during the AMP 6 period (201 5–2020) and all
schemes in the region are proceeding in line wit h agreed timescales with
the exception of a scheme in Brist ol W ater to renovate trunk mains to
secure iron compliance. This scheme has bee n delayed due to street
works restrictions result ing in a f ive -month delay to overall complet ion ,
which was achieved in October.
By way of comparison, in 2015, local aut horit ies in the W estern region put
in place 73 improvement Notices in relat ion to f ail ing private water
supplies.
The requirement f or companies to complete a risk assessment f or ever y
treatment works and supply system was init iated as part of the 2007
amendments to the Regulations. In October 2015, the Inspectorate
completed its project f or a database, which sets a commonly agreed
f ramework f or summary r isk assessment reports demonstrating company
compliance with the Regulations. The dat abase collects risk inf ormation
associated with catchments, treatment works, service reser voirs and
zones, and lets the I nspector ate scrut inise those risks and related
mitigations. The Inspectorate’s assessment of the risk inf ormation and any
result ing enf orcement action is also visible . This key change embraces the
principles of risk assessment and better reg ulation. The database makes
inf ormation available in expectat ion of the transposit ion of Annex II of the
Drinking W ater Directive late in 2017. Annex II permits the variation of
sampling f requencies based on the outcome of the risk assessment. W ork
is currently ongoing to develop the outcomes of the assessments and this
will be taken into account in the risk -based response of the Inspector ate
going f orward.
The Inspectorate pr ovided the water industry with technical advice on six
topics to enable wat er supp liers to comply with the drinking water
regulations. In addit ion , eight resear ch pr ojects were published by the
Inspectorat e to develop under pinning knowledge f or regulatory r isk
assessments. Annex 2 lists all of the advice and research published by the
Inspectorat e in 2015 .
9
Drinking water 2015
Chapter 2: Water supply arrangements
Chapt er 2:

Identif ies the water supply companies in the region .

Illustrates the water source and supply ar rangements in the region .

Provides summary f igures describing the water supply assets and
stakeholders.
Figure 4: Map illust rating sources of drinking w ater by zone across
the region
Seven water companies supply dr inking water in the W estern region:
Bristol W ater (BRL); Bournemouth W ater (SBW ); Cholderton and District
W ater (CHO); South W est W ater (SW T); and W essex W ater (W SX),
including two inset appointees: Veolia W ater Projects (VW P) supplies
consumers in the Tidworth area; and SSE W ater (SSE) supply consumers
in Old Sarum, Salisbury; Br ewer y Square, Dorchester and Em ersons
Green, Bristol.
10
Western region
Much of the water in the region or iginates f rom surf ace water (71%)
abstracted f rom river s such as the Severn, the Hampshire Avon, Dart, Exe,
Fowey, Tamar and the Dorset Stour. There is a major transf er of water into
the region via the River Sever n f rom re servoirs in W ales that provide half
the daily supply f or consumers in England in the Br istol W ater area.
Additionally, the upland areas of Bodmin Moor, Dartmoor, Exmoor and the
Mendips are important catchments f or water resources in the region.
Surf ace wat er is drawn f rom many reser voirs, including Chew Valley Lake,
Clat worthy, Collif ord, Roadf ord and W imbleball. Groundwater also pr ovides
a valuable resource (27%) in the region, with most boreholes drawing
water f rom the chalk aquif er of the W essex basin. C holderton and District
W ater is reliant exclusively on the chalk aquif er of the W essex basin. The
Permian and Triassic sandstone aquif er in the Otter Valley is another
valuable groundwater resource in East Devon. Acr oss the region, a small
proport ion of wa ter supplies (2%) can be drawn f rom either surf ace or
groundwater sources.
Private water supplies in the region ar e widely distributed across the area,
but are more concentrated in East Devon and Cor nwall. These privat e
supplies are more reliant on groundw at er (47%) than the public supplies in
the area (27%). For more inf ormation about private wat er supplies please
ref er to Drinking w ater 2015 – Private water supplies in England .
Figure 5 illustrates the location of privat e and public supply groundwater
abstraction points in relat ion to the groundwat er aquif ers in t he region.
11
Drinking water 2015
Figure 5: Location of private and public suppl y groundw ater
abstraction point s
Summar y f acts about the drinking water supply inf rastructure of the region
are given in Table 6 with outline geographical and demographic
inf ormation.
12
Western region
Table 6: Key fact s about public and private w ater suppl y arrangements
in the Western regi on
Public supplies
Private supplies
Population supplied
Water supplied (l/day)
4,689,045
1,258 million
Abstraction points
Treatment works
Service reservoirs
Water supply zones
Length of mains pipe (km)
361
148
780
162
36,424
Water composition
Surface sources
Groundwater sources
Mixed sources
71%
26.5%
2.5%
Population supplied
Water supplied (l/day)
Approximate number of private
water supplies*
Total number of local
authorities
Number of local authorities
with private supplies
Water composition
Surface influenced supplies
Groundwater sources
Mains water
Unknown
340,856
107 million
13,285
30
26
16%
47%
37%
0%
Area of supply
Cornwall, Devon, Dorset, Gloucestershire (part), Hampshire (part), Somerset and Wiltshire
(part).
*Boundaries for public supplies regions are based on groupings of water company zones.
Boundaries for private supplies figures are based on the closest approximation of the public
supply zones. Where local authorities’ boundaries cross regional boundaries, the whole local
authority data has been attributed to the region in which the majority of its area lies.
13
Drinking water 2015
Chapter 3: Drinking water quality testing
Chapt er 3:

Explains the basis of the drinking wat er testing programme.

Recor ds the number of tests carried out by water companies.

Identif ies any def iciencies in water test ing and how these have been
remedied.
Throughout 2015, water companies sampled drinking water across the
region to ver if y com pliance with the dr inking water regulations. One-third
of the tests were carried out on samples drawn f rom consumers’ taps
selected at random. For monitor ing purposes, company water su pply areas
are divided into zones. Sampling in zones at consumers’ taps is risk -based
with the number of tests being higher in zones with a large population
(maximum 100,000). Other sample locat ions are water treatment works and
treated wat er (ser vice) res er voirs. Collectively, the seven water companies
carried out a total of 590,840 tests dur ing 2015 and o nly 99 of these tests
f ailed to meet one or more of the standards set down in the Regulations or
exceeded a screening value.
Table 7: Number of tests ca rried out by companies in the region
Comp an y
B our n em out h
W ater
Pl a ce of s a mpl ing
W at e r
Con sum e rs ’
S erv ic e
t r eat me nt
tap s
re s e rv oi rs
w ork s
(z one s)
13 , 46 0
6, 0 16
18 , 97 5
( 7)
( 20 )
( 10 )
Numb e r of
tes ts p er
com pa n y
T arg et
numb e r of
tes ts
38 , 45 1
38 , 62 5
26 , 33 9
( 17 )
49 , 43 0
( 16 5)
44 , 15 9
( 27 )
11 9 ,9 2 8
12 0 ,4 3 6
39 5
( 2)
31 2
( 1)
35 7
( 1)
1, 0 64
1, 0 66
50 , 93 1
( 31 )
79 , 94 4
( 26 6)
70 , 07 7
( 32 )
20 0 ,9 5 2
20 1 ,0 1 7
0
( 0)
0
( 0)
1, 4 67
( 3)
1, 4 67
1, 4 68
1, 2 64
( 2)
1, 3 00
( 5)
44 4
( 1)
3, 0 08
3, 0 08
W es s ex
W ater
69 , 73 9
( 68 )
92 , 92 5
( 30 4)
63 , 30 6
( 88 )
22 5 ,9 7 0
22 6 ,3 7 7
Reg ion
ov er a ll
16 2 ,1 2 8
( 12 7)
22 9 ,9 2 7
( 76 1)
19 8 ,7 8 5
( 16 2)
59 0 ,8 4 0
59 1 ,9 9 7
Br is t o l W ater
Ch o ld er to n
an d D is tr ic t
W ater
S ou th W es t
W ater
S S E W ater
V eo l i a W a ter
Pr oj ec ts Lt d
N u m b e r s i n b r a c k e t s r e f l e c t t h e n u m b e r o f wo r k s , r e s e r v o i r s o r z o n e s o p e r a t e d b y t h a t c o m p a n y
in the region in 2015. Some companies are permitted to carry out some tests on samples taken
from supply points rather than from consumers’ taps.
14
Western region
The Regulat ions set out the parameters t o be tested f or by water
compan ies. Most of the testing is f or parameters with a European or
national standard (Schedule 1 parameter s) , however, water companies are
also required by t he Regulations to test for other indicator parameters
(Schedule 2 par ameters). The Regulat ions also lay down how many of
these tests must be done each year (Schedule 3) and the Inspectorate
checks that the water companies are meeting these sample f requencies.
In 2015 ther e was a notable reduction in the number of works f or W essex
W ater f rom 79 in 2014 to 68 in 2015. This is a result of a strategic
initiative by the com pany manage down the risk of those sites , (see
Chapt er 4: Microbiological quality – Turbidity at works).
Across the region in 2015 the Inspect orat e f ound f rom its checks that there
was a shortf all in the number of test results submitted by six of the
companies in the reg ion.
Bristol W ater (518) , Cholderton W ater (2), Bournemouth W ater (174), SSE
W ater (1), South W est W ater (65), W essex W ater (407) , wer e unable to
provide test results f or analysis. These were due to a combination of
reasons including f ailing to revise the sample programme when a works or
reser voir is out of supply, ( 10 BRL, 1 CHO, 10 SBW , 4 W SX); f ailure to
schedule or reschedule samples ( 308 BRL, 1 SBW , 49 SW T, 233 W SX,);
errors or qualit y f ailures during analysis, ( 1 CHO, 20 SBW , 1 SSE, 8 SW T,
134 W SX); late submission of data to DW I ( 116 SBW , 20 WSX); or IT
problems ( 129 BRL).
South W est W ater reported sample data for tritium in error due to
miscoding of operational samples in Fe br uar y (32). Statutor y sampling f or
this par ameter is not required as the company has established, by r isk
assessment that monitor ing f or tritium is not required.
Companies are reminded to meet the dut ies placed upon them by
regulations and that senior ma nagers should be taking steps to satisf y
themselves, through regular internal reports, that the sampling programme
and the systems are being actively managed. W ithout all data, there
cannot be a complet e assessment and as a result, loss of conf idence in
the company perf ormance. Th is necessitated the ser ving of Final
Enf orcement Orders f or two companies in the Southern region requiring
the appropriate submission of all data in the f orthcoming year. Further
details can be seen in Drinking water 2015, Souther n region.
In October 2015, the European Commission adopted and published
replacement Annexes II and III to the Drinking W ater Directive. These
changes perm it the option of moving away f rom statutory minimum
f requencies of sampling f or a set list of paramete rs, introducing a risk based approach of determining which par ameters to monitor and at what
15
Drinking water 2015
f requency. The change in f requency, removal or addition of parameters is
intended to be based upon histor ical monitoring data f rom f inal and raw
water as well as r isk assessments and will bring the advantag e of
companies not having to unnecessar ily carry out analysis and to
concentrate on controls that pr otect public health. The development of the
Inspectorat e’s own r isk -based methodology will help determine if the
company application of these principles is being adopted. It will f urther
seek to ident if y an understanding of company risk, based upon a changing
dataset. The Inspectorate will communicate this changing strategy in
f uture Chief Inspector reports.
As an a dditional change to the Drinking W ater Directive, Annex III
introduces new accepted standards f or methods of analysis f or
microbiological parameters and changes def ined perf ormance
character ist ics f rom ‘Trueness’, ‘Precision’ and ‘limit of detection’ to
‘Uncertaint y of Measurement’. The DW I has a programme in place f or the
transposition of these requirements scheduled f or October 2017.
16
Western region
Chapter 4: Drinking water quality results
Chapt er 4:

Provides details of tests f ailing to meet microbiol ogical and chemical
standards.

Comments on the remedial act ion taken by the wat er company or the
Inspectorat e.
The key water qualit y results f or the W estern region are pr esented in t wo
tables, one showing the results f or microbiological parameter s (Table 8),
the other dealing wit h chemical and physical parameters (Table 12). The
microbiological quality of water is discussed f irst. Companies report all the
results of the tests on a monthly basis to the Inspector ate. A summary of
the results of testing f or all parameters and tables that describe the
drinking water quality perf ormance indices of each company can be f ound
on the DW I website ( www. dwi.def ra.gov.uk ).
Microbiological quality
To protect public health, micr obiological standards have to be met at ea ch
individual treatment works and ser vice reser voir. The signif icance of the
individual test results f or each microbiological parameter at each locat ion
var ies and a single posit ive result cannot be int erpreted wit hout other
inf ormation. All com panies are expected to f ollow best pract ice as set out
in The Microbiology of Drinking Water published by the Standing
Committee of Analysts (SCA) which can be f ound by visit ing the website at
https://www.gov.uk/government/publications/standing -committ ee-of analysts-sca- blue-books.
17
Drinking water 2015
Table 8: Microbi ological tests
The number of test s performed and the number of tests not meeting
the standard
P ar am et e r
Cu rr ent
st a nd ar d
T otal
numb e r
of t est s
Numb e r of
tes ts not
me eti ng
the
sta nd ar d
Ad di tio na l
info rm at ion
W ate r l e av ing w at e r t re at me nt w or k s
E.c o l i
0/ 1 00m l
22 , 85 6
0
Co l if orm b ac t er i a
0/ 1 00m l
22 , 85 3
4
BR L (1) SW T (3)
Cl os tri d i um
per fr i ng e ns
0/ 1 00m l
7, 3 79
1
W SX (1)
T urb id i t y
1NT U
W ate r l e av ing s e rv i c e r es e rv oi r s
22 , 83 0
3
SW T (3)
E.c o l i
0/ 1 00m l
38 , 37 3
4
0/ 1 00m l i n
95 % of t es ts
at e ac h
r es e r vo ir
38 , 36 6
26
1
Co l if orm b ac t er i a
W ate r s a mpl ed at co nsu me r s’ t a ps
E.c o l i
0/ 1 00m l
12 , 88 2
0
E nt er oc oc c i
0
1
0/ 1 00m l
1, 3 35
BR L ( 1) , SW T (2),
W SX (1)
BR L ( 2) , S BW (1),
SW T ( 13) , VW P
(2), W SX (8)
A l l 76 1 res er v o irs
i n th e r e g io n m et
th e 9 5%
c om pl i anc e r u l e
Tu r b i d i t y i s a c r i t i c a l c o n t r o l p a r a m e t e r f o r w a t e r t r e a t m e n t a n d d i s i n f e c t i o n .
E.coli at w orks and service reservoirs
In 2015, a total of 61,229 tests at works and ser vice reser voirs were
carried out by all of the comp anies across the region and E.coli was
detected in f our ser vice reser voirs (1 BRL, 2 SW T, 1 W SX). For the third
year in a row, there were no occurrences of E.coli in samples taken at
works.
On detecting E.coli, companies ar e required to act promptly t o pr otect
public health. Their immediate response when f inding E.coli at a works is
to sample again, and more widely, to conf irm that water being received by
consumers is saf e.
There were t wo events notif ied by South W est W ater concerning E.coli in
samples taken at ser vice reser voirs . These were at Bosavern ser vice
reser voir, near Penzance, in July (see Annex 3), and Cor onation Park
ser vice reser v oir, near W adebridge, in August (see Annex 3). Both
reser voirs wer e int ernally inspected. The Bosavern ser vice rese rvoir was
18
Western region
f ound to be structurally sound and no ingress was identif ied. The company
carried out enhanced monitor ing f or six weeks prior to returning it to
supply, all sample results were sat isf actory. At Coronat ion Park service
reser voir ingress was identi f ied (a hair line crack in the wall and a small
area near one of the roof hatches). This was repair ed and samples taken
since the reser voir was returned to supply have been sat isf actory.
Identif icat ion by W essex W ater of E.coli at Bratton Seymour New ser vice
reser voir, near W incanton, in September was not if ied to the I nspector ate
as an event: (see Annex 3). The cause was identif ied as ingress along a
cable duct allowing mice to enter the reservoir compartment. A boil water
notice was issued f or the properti es downstream until this ingress was
f ixed. The Inspector ate visited the site t o ensure that the act ions taken
were appropr iate.
Bristol W ater identif ied E.coli in a sample taken at the Dial Hill -1b-Ot
ser vice reser voir, in Clevedon, in October. This was reported as an event
(see Annex 3). Inspection revealed some ingress risks, which were
remedied. The company also conducted an audit of the laboratory. The
audit revealed some issues, which the company consider minor and
unlikely to cause the posit ive resu lt. The company have been unable to
determine a def initive cause f or the detection of E.coli.
Table 9: Detection of E.coli and Enterococci at treatment w orks,
service reservoirs and consumers’ taps
Comp an y
E. co li i n
w at er
le av in g
t r eat me nt
w ork s
E. co li i n
w ater
le av in g
se rv i c e
re s e rv oi rs
E. co li a t
con su me r s’
tap s
Ent e ro co cc i
at
con su me r s’
tap s
B our n em out h
W ater
0 – 1 ,7 5 5
0 – 1 ,0 0 4
0 – 1 ,1 0 3
0 – 99
Br is t o l W ater
0 – 3 ,7 3 3
1 – 8 ,2 3 8
0 – 3 ,1 6 5
0 – 2 52
0 – 55
0 – 52
0 – 12
0 – 4
0 – 7 ,2 2 5
2 – 1 3, 3 28
0 – 4 ,4 8 3
0 – 3 83
0 – 0
0 – 0
0 – 36
0 – 12
0 – 2 08
0 – 2 60
0 – 24
0 – 8
W es s ex W ater
0 – 9 ,8 8 0
1 – 1 5, 4 91
0 – 4 ,0 5 9
0 – 5 77
Reg ion ov er al l
0 – 2 2, 8 56
4 – 3 8, 3 73
0 – 1 2, 8 82
0 – 1 ,3 3 5
Ch o ld er to n a n d
Dis tr ic t W ater
S ou th W es t W ater
S S E W ater
V eo l i a W ater
Pr oj ec ts Lt d
Note: Results are shown as the number of positive tests – the total number of tests.
19
Drinking water 2015
Coliform bacteria at w orks
Testing f or colif orm bacteria gives reassurance that water entering supply
was treated adequat ely to remove bacter ial and viral pat hog ens. Repeated
occurrences of colif orm bacteria in samples f rom the same works in one
year are thus of concern and require act ion to be taken. In 2015, this
situat ion did not occur at any of the 148 works in the region, although
there were f our sites where a single detection of colif orms was reported.
In April, Br istol W ater notif ied the Inspect orate of an event concerning the
isolat ion of colif orms isolated in a sample from the Littleton works, near
Evesham (see Annex 3). Invest igations were unable to esta blish the cause
of the f ailure. Similarly no cause could be f ound f or a colif orm detected at
South W est W ater’s Dotton works, near Sidmouth in June, nor at their
Delank works, near Bodm in, in Sept ember, despite invest igation.
Enhanced monit oring was undert aken at all sit es and all sam ple results
were sat isf actory.
W here no cause was f ound f or a f ailur e or where the company response
does not provide adequate reassurance of a low r isk of f urther f ailures,
this will be taken int o account dur ing the Inspectorat e’s own assessment of
the company r isk.
Following the detect ion of a colif orm in December at South W est W ater's
Pynes works near Exeter, the chlorine contact tank and treated water
tanks wer e subject ed to an internal inspection which identif ied a point of
ingress at a hatch on the roof of the treated water tank. The hatch was
subsequently repaired and all resamples were sat isf actory.
The Inspectorate has noted that colif orm bacteria were f ound in f our
samples f rom treatment works in the W estern region dur ing the year . This
inf ormation will be taken into account dur ing the Inspectorate’s risk -based
programme of technical audit.
Clostridium perfringens
This organism is a spore-f orming bacterium that is exceptionally resistant
to unf avour able conditions in t he water environment, such as extremes of
temperature and pH, and disinf ection pr ocesses such as chlor inat ion and
ultraviolet light. It is a normal component of the intestinal f lora of up to
35% of humans and other warm -blooded animals. These char acterist i cs
make it a usef ul indicator of either inter mittent or hist orical f aecal
contamination of a groundwater source or the perf ormance of a surf ace
water f iltration plant. The detection of any Clostridium perfringens should
trigger an invest igation by the wate r com pany.
20
Western region
In Februar y, W essex W ater reported a single Clostr idium perf ringens in a
f inal water sample f rom Cattistock works, near Dorchester, where the
works was perf orming satisf actorily at the time and no other def init ive
cause was f ound . Through enhanced sampling , deterioration in raw water
qualit y was identif ied and t he works was removed f rom supply. There are
currently no plans to return the source to service without additional
treatment. This illust rates the use of an evidence -based investigation to
identif y r isk and a posit ive response where this changes.
Turbidity at w orks
Turbidit y is a measure of how much light can pass through water and
indicates the ‘cloudiness’ of water. Turbidit y may be caused by either
inorganic or organic particles suspende d in the water. At a treatment
works turbidit y is an important cr itical control in relation to determining
whether raw water has been adequately prepared f or disinf ection. Turbidit y
standards are set at two points in the wat er supply chain, at treatment
works and at consumers’ taps. The f ollowing discussion f ocuses on the
results of samples taken at treatment wor ks wher e the standar d is 1 NTU.
The results of turbidity test ing at consum er s’ taps can be f ound in the
Maintaining w ater quality in distribution section.
Groundw ater w orks
W here turbidity arises in groundwater it is usually as a consequence of
disturbance of inert clay or chalk particles , but it can also arise f rom the
oxidation and precipitation of certain inorganic substances like iron and
manganese when air is introduced into the water by pumping. If the
groundwater is under the inf luence of surf ace water then the cause of
turbidit y may be part icles with adherent biological matter, which may
contain pat hogens.
Irrespective of origin, turbidit y can interf ere with the eff iciency of
disinf ection. Turbidit y is theref ore a crit ical control measure t hat should be
validated at a groundwater works by continuous on - line monit oring of raw
water with alarms set to ensure that act ion is taken to guarant ee that
turbidit y is <1NTU at all times. W here a risk f rom Cryptosporidium has
been identif ied in relation to a groundwater source and its catchment, then
companies should be carr ying out monit oring of the raw wat er and this
should be taken into account when deter mining the nature of the risk and
the suff iciency of the control measures.
Table 10 illustrates t he potential groundwater Cryptosporidium risk in the
region and compares it to the actual Cryptosporidium risk in 2015. Out of a
total of 202 groundwater raw w at er abstr action points where data wer e
submitted, 45 wer e subjected to r isk -based monitor ing f or Cryptospor idium
21
Drinking water 2015
and the r isk was ver if ied by positive oocysts detections at only 12
abstraction points serving the f ollowing treatment works ; W oodgreen
(SBW ), Corscombe, Dewlish, Dunke rton, Hooke, Sutton Poynt z, W ashpool
(W SX). None of these groundwat er works exhibited a turbidit y value higher
that 1NTU in 2015.
Table 10: Crypt osporidium risk assessment and monitori ng of
groundw ater abstraction points in the Western regi on in 2015
Numb e r of r aw
w at er m onit or ing
point s w h er e da ta
sub mit t ed
Numb e r of
ab str a cti on
point s w h er e
raw w at er i s
monit o red fo r
Cr ypt osp or id ium
Numb e r of
ab str a cti on poi nts
w her e ri s k of
Cr ypt osp or id ium w as
v er ifi ed * b y th e
det ect ion of oo c yst s
B our n em out h
W ater
10
1
1
Br is t o l W ater
13
13
1
2
0
0
28
0
0
3
1
0
W es s ex W ater
14 6
30
10
Reg ion a l tot a l
20 2
45
12
Indu st r y tot a l
1, 6 01
42 0
31
Comp an y
Ch o ld er to n a n d
Dis tr ic t W ater
S ou th W es t
W ater
V eo l i a W ater
Pr oj ec ts Lt d
*verified means either positive detection of Cryptosporidium oocysts or data quality insufficient.
Unclear data is assumed to be positive.
Kersbrook works (SW T) exper ienced a t urbidit y f ailure in Januar y due to a
change in f low f rom the borehole result ing in the dist urbanc e of f ine
particulate matter in the borehole and disturbance of settled deposits in
the pipework bet ween the headworks and the f inal monitoring point. This
was not if ied as an event to the Inspector ate (see Annex 3).
Four sites in W essex W ater’s areas (W int erbourne Abbas, Co rscombe,
Milborne W ick and Boyne Hollow) were permanent ly closed in 2015.
W essex W ater has a programme of work agreed at 24 addit ional
groundwater sites ( t en of which were agr eed in Februar y 2016) to manage
risks relat ing to turbidit y an d Crypt ospor idium . The works relates to
var ious rehabilitat ion schemes at the sit es, including measures to allow
the sites to run to waste, improve and continue on - line monit oring of water
22
Western region
qualit y, make more robust the automated f acilit y f or sites to shut down. At
some of the sites the company is also making improvements t o the
pipework on site and to integrit y of the boreholes and disinf ection
processes.
The programme of work and the removal of sites f rom supply by W essex
W ater is illustrated by Table 10 wher e the number of abstraction points is
reduced by 25% over 2014 whil e the monitoring f or Cryptosporidium has
increased by 30%, yet the number of detections has halved. The
company’s use of risk assessments to evaluate f ailur e of turbidit y and
Cryptospor idium as reported in Dr inking water 2014 and bef ore has
determin ed a f orwar d thinking strategy. This strategy illustrates the
successf ul combination of network resilience object ives while ensur ing
water qualit y is the primar y outcome.
Surface w ater w orks
Turbidit y in surf ace water is related to sediment and biological matter.
Following rainf all the f low and hence the t urbidit y in rivers and streams
can rise ver y quickly and values in excess of 100NTU are not uncommon.
Surf ace water may be abstracted into reservoirs wher e storage of the
water allows particles to settle out; however, some of these reser voirs do
not have a suff iciently long retent ion t ime f or settlement of pathogens such
as Cryptospor idium . All surf ace waters are likely to cont ain some f aecal
matter originat ing f rom animals, birds and sewage works discharges. For
this reason, surf ace water must be prepared f or disinf ection (clar if ication
and f iltration). The Bouchier report recommended continuous turbidit y
monitor ing af ter f iltration at surf ac e water works against a perf ormance
target f or each individual f ilter of <1NTU. Since turbidit y can interf ere with
the eff iciency of disinf ection, it is a crit ical control measure t hat should be
validated by continuous on - line monitor ing of f iltered water with alarms set
to ensure that action is taken to ensure t hat turbidit y in water entering the
f inal disinf ection stage is <1NTU at all times. W here a risk f rom
Cryptosporidium has been identif ied in the catchment upstream of the
abstraction point, then com panies should be carr ying out monitor ing of the
raw wat er and this should be taken into account when deter mining the
nature of the risk and the suff iciency of the control measures.
Table 11 illustrates t he potential surf ace water Cryptospor idium risk in the
region and compares it to the actual Cryptosporidium risk in 2015. Out of a
total of 79 surf ace water raw wat er abstr action points (or monitor ing points
f or sources inf luenced by surf ace water) where data were submitted , 59
were subjected to r isk -based monitor ing for Cryptosporidium and the risk
was ver if ied by positive oocysts detections at 44 abstraction points ser ving
the f ollowing treatment works: Banwell, Barrow, Cheddar, Littleton, Purton,
23
Drinking water 2015
Stowey ( BRL); Alder ney (SBW ); Allers, Avon, Bastreet, Bratto n Flem ing,
Crownhill, De lank , Dousland, Drif t, Horedown, Littlehempston, Lower Moor,
Northcombe, Prewley, Pynes, Restormel, St Cleer, Stithians, Tamar,
Venf ord, W endron (SW T); Corf e Mullen, Durleigh, Fulwood, Maundown,
Sutton Bingham, Tucking Mill, Upton S cudamore (W SX). None of these
works exhibit ed a tur bidit y value of higher than 1NTU in 2015.
Table 11: Crypt osporidium risk assessment and monitori ng of surface
w ater abstraction points in the Western region in 2015
Numb e r of r aw
w at er m onit or ing
point s w h er e da ta
sub mit t ed
Numb e r of
ab str a cti on
point s w h er e
raw w at er i s
monit o red fo r
Cr ypt osp or id ium
Numb e r of
ab str a cti on poi nts
w her e ri s k of
Cr ypt osp or id ium w as
v er ifi ed * b y th e
det ect ion of oo c yst s
B our n em out h
W ater
6
3
3
Br is t o l W ater
8
7
5
Comp an y
Ch o ld er to n a n d
Dis tr ic t W ater
S ou th W es t
W ater
V eo l i a W ater
Pr oj ec ts Lt d
0
0
0
29
29
25
0
0
0
W es s ex W ater
36
20
11
Reg ion a l tot a l
79
59
44
Indu st r y tot a l
42 8
27 4
20 8
*verified means either positive detection of Cryptosporidium oocysts or data quality insufficient.
Unclear data is assumed to be positive.
South W est W ater reported a f ailure f or turbidit y at their Tottif ord works,
near Bovey Tracey, in July, and another in October. These were due to
issues with lime dosing post -disinf ection where the re lative posit ions of the
lime plant and dosing point le d to siphoning of lime on works shutdown.
Valving to prevent this has been installed as an interim measure , prior to
completion of a current scheme f or upgrades at this site to be completed
by 2019. The risk assessment at this site has been amended.
Bournemouth W ater currently has legally-binding programmes of work
relat ing to Cryptosporidium at the Alder ney and Knapp Mill wor ks, where
UV has been installed and the exist ing f ilters will be inspected and
upgraded as necessary . This programme is on track f or delivery in 2020.
24
Western region
There are a f urther two programmes of work f or Cryptosporidium and
turbidit y; one f or the development of a new works at Ro borough in South
W est W ater’s area and the second f or UV inst allat ion at Brist ol W ater’s
Barrow works. These programmes are on track f or completion in 2021 and
2017 respect ively.
Coliform bacteria at service reservoirs
Testing f or colif orm bacteria gives reassurance that the quality of water
held at these strateg ic points in the distr ibution system is adequately
maintained. The national standard requir es that at least 95% of no less
than 50 sam ples collected f rom each ser vice reser voir throughout one year
are f ree f rom all colif orm bacteria. In 2015, all ser vice res er voirs (including
water towers) in the region met the standard.
W hen South W est Water identif ied colif orms at Belliver ser vice reser voir,
in Plymouth, in April, invest igation led to the replacement of the sample
tap af ter a leak was f ound.
Also in Apr il a single colif orm was isolated f rom a sample taken at South
W est W ater’s Tregadille tt ser vice reser voir, near Launceston. The most
likely cause of the f ailure was related to t he minor integrit y issues
identif ied during an internal inspect ion. The roof membr ane was replaced
and extended bef ore this reser voir was r eturned to supply.
In May, there was a colif orm f ailure at Bristol W ater’s Pucklechurch
ser vice reser voir. No def inite cause could be attributed to this f ailure. The
ser ving treatment works and rela ted sampling carried out on the same day
were all satisf actory. The reservoir was cleaned and chlorinated bef ore
being put back into service.
W heddon Cross No 1 ser vice reser voir, near Minehead, suf fered a colif orm
f ailure in May. At the time of sampling t here was torrent ial rain and the
sampling point was overgrown with veget ation which could have
contributed to the f ailure. W essex W ater cut back the vegetation around
the sample point. Inspection of the reser voir revealed no ingress. A
permanent booster ch lor ination f acilit y has been installed upst ream f rom
this reser voir at Timberscombe pumping station .
South W est W ater carried out an inspect ion of Bi ckington ser vice
reser voir, near Newt on Abbot, in July af ter colif orms wer e detected. Two
sources of ingre ss were identif ied and rectif ied. The reser voir remains out
of service and will most probably be abandoned af ter a period of proving
the net work is robust without it .
W hen a colif orm f ailure was detected at Marshwood ser vice r eser voir, near
Charmouth, in July, W essex W ater drained and inspected the reser voir,
25
Drinking water 2015
f inding no structural def ects but leaking hatch seals. These were resealed,
inspected and f lood t ested. The reser voir was then cleaned, f illed,
sampled and returned to ser vice.
South W est W ater’s inv estigat ions of colif orm f ailures at Ant ony ser vice
reser voir, near Saltash and Ashwell ser vice reser voir, near Teignmouth, in
July did not show any ingress. The reser voirs were cleaned and returned
to supply. Samples from both reser voirs have been sat isf ac tory since this
work. Similar ly no def inite cause could be f ound f or a colif orm f ailure at
Landscore ser vice reser voir in south Devon in October.
At Sway ser vice reservoir, there was a colif orm f ailure in July. There were
previous f ailures in 2009, 2012 an d 2014 at this site. Bournemouth W ater
took the off ending cell out of supply. Internal inspect ion identif ied a crack
in the f loor which has been repair ed but the reser voir remains out of
ser vice await ing installat ion of new sampling f acilit ies. The rese r voir is
within the New Forest N ational Park and as such is subject to strict
planning control which means that this may take some t ime to arrange. In
the meantime the second cell of this structure will be able to sustain
supplies.
At Hampton Down service re ser voir, near Bath, in response to a colif orm
f ailure in July, W essex W ater reported that inspection raised a number of
minor issues, although no ingress or any other obvious cause was
identif ied.
August was the month with the highest number of f ailures f o r colif orms at
ser vice reser voirs, m any wer e associated with heavy rainf all in the region
as f ollows:
W essex W ater detected colif orm bacteria in a sample collect ed f rom
Knapps Hill ser vice r eser voir, near Sherbourne. Investigation showed
ingress through a cr ack in the roof of the inlet chamber and perishing
seals around hatches and access chambers. The seals were addressed
and the inlet chamber has been abandoned.
Following a colif orm f ailure at Haz eldown service reser voir, in Teignmouth,
in August , inspection revealed ingress. South W est W ater removed the
aff ected cell of the reser voir f rom supply and it will remain out of service
until the necessar y remedial actions have been taken to repair the
structure.
Companies should develop an appr opriat e inspect ion based upon risk to
identif y ingress bef ore rain identif ies this f or companies through f ailures.
Matthew Tank service reser voir, near Tidworth, suf f ered a colif orm f ailure
f rom each of the two cells in August. Veolia W ater Projects considers that
26
Western region
these f ailures are due to taking the samples at exposed sample taps
during heavy rainf all. A new kiosk is to be installed to ensur e that the
sampling f acilit y is not exposed to the elements or external contaminants.
In the meantime, modif icat ions to the existing sample point and weekly
cleaning have signif icantly reduced the r isk of a non -compliant sample at
this f acilit y.
Also in August, W essex W ater’s investig ation of a colif orm f ailure at
Heathcombe ser vice reser voir, near Br idgewater, showed that the samplin g
kiosk was overgrown with vegetat ion, which has now been cut back.
Inspect ion of the reservoir showed no evidence of ingress. This is the thir d
year running with colif orm f ailures at this site and, while the company are
consider ing long -term options f or t his reser voir , the Inspectorate have
initiated enf orcement to ensure act ion is taken to reduce any residual risk.
Companies are reminded that sampling facilities must be suit able f or use
at all times including during inclement weather and appropriate
maintenance, design and if necessar y replacement as part of ongoing
planning.
Colif orms were det ected at Newquay Road ser vice reser voir, near Truro, in
September. South W est W ater inspected the reser voir, minor cracks in the
walls were repaired and the reser vo ir returned to supply. All samples have
been satisf actor y since this work and the sampling f acilities at this sit e
were upgraded in 2016.
Following a single colif orm detection in a sample taken at the Burstock
ser vice reser voir, in west Dor set , in October showed only m inor hatch
leaking which W essex W ater repaired – all samples have been satisf actor y
since.
W essex W ater’s Dancing Hill No.2 reser voir near Bridg water was the site
of a colif orm isolation in October. The reser voir was removed from supply
f or a f ull inter nal sur vey in Januar y 2016, which ident if ied poor seals
around the old telemetry probe heads which could be potent ial points of
ingress. The probes were removed and holes sealed bef ore returning the
structure to ser vice.
An inspection was carrie d out at Upton service reser voir, near
Kingsbr idge, af ter a single colif orm was detected in a sample taken in
December dur ing a rainstorm. No ingress was f ound on inspection ,
although a leaking roof on the sample tap kiosk will be replaced to protect
the samples at times of bad weather. Similarly the sample cabinet was
replaced af ter isolat ion of a single colif orm in a sample taken in December
at the Ashburton ser vice reser voir, near Newt on Abbot.
Also, in December , a colif orm f ailure was detected at the D anes Cast le
(New) reser voir in Exet er. Inspect ion of the reser voir showed no ingress
27
Drinking water 2015
and all samples taken in enhanced sampling since then have been
satisf actor y. This f ailure may be associat ed with an earlier f ailure at the
upstream Pynes wor ks due to a l eaking hatch cover in the f inal water tan k
which has been repaired.
In Drinking Water 2014 it was reported that f our service reser voirs were
due f or abandonment. South W est W ater has abandoned W embur y ser vice
reser voir, near Plym outh , Ashcombe ser vice rese r voir, near Dawlish and
Haytor ser vice reser voir, near Bovey Tracey. W essex W ater abandoned
W yke service reser voir in W eymouth in November .
The Inspectorate has noted that colif orm bacteria were f ound in 26
samples f rom service reser voirs in the W estern region during the year and
this inf ormation will be taken into account during the Inspectorate’s r isk based programme of technical audit.
E.coli and Enterococci at consumers’ taps
A total of 12,822 consumer s’ taps were tested in 2015 f or E.coli and all
gave sat isf actor y results. Like E.coli, the presence of Enterococci is
indicative of f aecal contamination and neither bacter ium should be f ound
in any sample. In 2015, the companies carried out 1,335 tests f or
Enterococci at consumers’ taps , none of which ga ve a posit ive result .
Chemical quality
The drinking water r egulations set out the minimum testing requirements
f or all chem ical and physical param eters. A f ull summar y of the results of
testing by each com pany, including the r esults f or indicator paramet ers, is
provided on the DW I website.
The f ollowing text and Table 12 set out the results f or those parameters
where there has been a f ailure to meet a European or national standard
(mandator y qualit y standards) and any ot her parameter of int erest. In
addition, at the request of local author ities, the results of testing f or
f luoride, iron, lead, manganese, nitrate, nitrit e, pesticides and radioact ivity
are given. The Inspectorate has also included instances wher e residual
chlorine results were reported at a level t hat may be consider ed
undesirable on grounds of consumer acceptabilit y (2mg/l).
28
Western region
Table 12: Chemical and ph ysical parameters
The number of test s performed and the number of tests not meeting
the standard
Total
number
of tests
Number of
tests not
meeting
the
standard
4,056
7
4,024
9
200μg/l
4,739
2
BRL (3), SWT (4), WSX
(2)
BRL (1), WSX (1)
2mg/l
12,755
2
BRL (1), WSX (1)
2mg/l
12,815
2
BRL (1), WSX (1)
2mg/l
1,410
1
SWT (1)
Fluoride
1.5mg/l
1,270
0
Iron
200μg/l
4,602
13
Lead
10μg/l
1,350
7
BRL (6), SWT (5), WSX
(2)
BRL (1), WSX (6)
Manganese
50μg/l
4,643
2
BRL (1), SWT (1)
Nickel
20μg/l
3,702
6
BRL (2), WSX (4)
Nitrate
50mg/l
1,699
0
Nitrite
0.5mg/l
1,701
0
0.5μg/l
1,868
0
0.1μg/l
26,994
0
0.1Bq/l
302
0
1.0Bq/l
287
0
0.1mSv/year
0
0
100Bq/l
183
0
Current
standard or
specified
1
concentration
Parameter
Additional information
Aesthetic parameters
– odour
No abnormal
change
– taste
Aluminium
Chlorine – residual (free)
Chlorine – residual
2
(total)
Copper
Pesticides – total
3
Pesticide – individual
2
BRL (3), SWT (4)
Radioactivity
Gross alpha
Gross beta
4
4
Total indicative dose
Tritium
Notes:
1
For comparison, 1mg/l is one part in a million, 1μg/l is one part in a thousand million.
2
The value of 2mg/l at the consumer’s tap is a screening value set by the Inspectorate.
3
A further 747 tests were done for aldrin, dieldrin, heptachlor, heptachlor epoxide, all of which met the relevant
standard of 0.03µg/l.
4
These are screening values to trigger action. The standard is ‘Total indicative dose’.
29
Drinking water 2015
Aesthetic parameters
Aesthetic parameters : Taste and odour
Consumers expect their dr inking water t o be clear and bright in
appearance and f ree from discernible taste or odour. In recog nit ion of this
the Regulations st ipulate national standards f or colour, odour and taste.
Companies are required to investigate the cause of any adver se result.
In 2015, a total of 12 samples f rom consumers’ taps in the reg ion exhibited
a positive taste or odour. All tests in the region met the st andard f or
colour.
The posit ive detect ions of taste and odour are summarised below in
relat ion to their nature and cause as determined by the invest igations
carried out by the companies. From this inf ormation it can be seen that
many were conf ined to a si ngle property and did not ref lect a wider
problem in the water supply zone.

Petrol/sol vent: (1 BRL) these descr iptor s relate to situat ions where
there has been a spillage of central heat ing oil, petrol or diesel on
the propert y and this has permeated thro ugh the plastic water supply
pipe, as occurred in this case; the remedy is to advise the
householder on the need to replace the aff ected pipe and to
saf eguard against f uture spills.. A sample taken in Br istol W ater’s
Thornbur y, Shirehampton, Pill and Port i shead zone in June reported
a petrol/solvent odour . This was f ound t o be due to the perm eation
of hydrocar bons thr ough MDPE supply pipe which has since been
replaced with suit able barrier pipe.

Bitter/Flat: (2 BRL, 2 W SX, 1 SW T) these descr iptors relate t o
samples where the t ap water was art if icially sof tened; the remedy is
to advise the householder to draw water f or drinking and cooking
f rom the tap connected dir ectly to the mains (or to f it a mains f ed tap
if one does not exist). A bitter taste in a rent ed home in the Allington
zone in May proved t o be due to sof tened water being supplied f or
drinking. W essex W ater served a Section 75 Not ice on the landlor d
and contravent ions were rect if ied. A visit f rom the company
conf irmed this.
In three other cases in W essex W ater’s Zeals zone in Septem ber
and the Fr ome, Nort on St Philip, Leigh -On- Mendip and Colef ord
zone in the Br istol W ater area in Apr il and October were all f ound to
be due to a water sof tener. The customer s were advised accordingly.
A sample in Sou th W est W ater’s Avon zone in Apr il exhibited a
metallic/ bitter taste. Investigation showed the presence of ver y low
levels of halogenated phenols and 2 -met hylmercaptobenzot hiazole
30
Western region
indicating an internal plumbing issue. A W ater Fittings Inspection did
not f ind anything unt oward. The mains were f lushed as a precaution
and all subsequent samples have been satisf actory.

Earthy/must y: (4 SW T) these descript ors relate to situat ions where
harmless, but object ionable, substances are produced by the growth
of algae in raw water storage reservoirs or the growth of f ungi in
poor ly designed plumbing systems; the remedy is improved
treatment/reser voir management by the company or to advise the
householder on necessar y changes to the design and maintenance
of the plumbing syst em. Failures were reported in f our of South W est
W ater’s zones (St ithians, Rest ormel, Prewley and Northcombe)
during August and September. These exceedances all occurred af ter
a period of sudden heavy rain causing an unprecedent ed rise in raw
water concentrat ions of methylisoborneol – over ten times the
previous maximum level. Temporary treatment was installed
although it took a number of weeks f or levels to be reduced t o below
taste thresholds. This temporar y treatment will remain on site until
the permanent installat ion of treatment is completed. This was
reported as an event . The works at Northcombe is undergoing
ext ensive improvem ents as part of an AMP 6 legal instrument ,
installing granular activated carbon pre f iltration and upgrading
disinf ection. The improvements will address taste and odour, THM’s
and also pesticide risks benef i ting just over 240,000 of consumers in
the area. This work will complete in 2019. Restormel works was
previously subject to a programme of wor k to address pesticides and
has GAC installed, which would also act t o mitigate against taste
and odour issues. The Inspector ate noted the unprecedented
challenge to raw water during 2015 , but expects the com pany to
update their r isk assessment to ensure f urther taste and odour
issues are mit igated. The perf ormance at this works will continue to
be monit ored to ensure that the scheme can demonstrate benef it.
Stithians works was also subject to an im provement program me to
address taste and odour and the company reported complet ion in
2012 (see Annex 3).

Soap y: (2 BRL) Bristol water ident if ied plumbing -related organics
causing a soapy/ lem on taste and odour in July in the W orle, W eston Super- Mare North and Central zone. A W ater Fittings Inspect ion was
carried out which did not identif y a s pecif ic cause, but some minor
problems which they helped the customer to rectif y. A second soapy
odour was reported in Bristol W ater’s Eastville, Easton, Netham and
St Philips zone in August. It is likely that the odour had developed in
the inter nal plumbi ng system while lying stagnant prior to sampling
due to the occupants being on holiday.
31
Drinking water 2015
Consumer contacts to w ater companies for taste and odour
W hen consumers experience a persistent taste or odour, they may contact
their water company to report the probl em. Records of these contacts in
each zone are recor ded by water companies and passed to the
Inspectorat e annually. Figure 13 shows t he zone by zone contact rate per
1,000 populat ion across the W estern region, and shows that the highest
rate of taste and o dour complaints occurr ed in W essex W ater’s Ashf ord
Stowey zone (4.1 complaints per 1 , 000 population – see Chlorine section).
Additionally three m ore of W essex W aters zones showed a high level of
complaints (Swanage (1.6/1 ,000 pop), Charmouth (2,2/1 ,000 pop), Dotter y
(1.6/1,000 pop)), as well as a zone in the Bournemouth W ater area
(W imborne zone 2.1/ 1 ,000 pop).
Figure 13: Rate of t aste and odour contacts per 1,000 people
Enf orcement action was taken by the Inspectorate in May 2015 in relat ion
to the occurrence of taste/odour in water supplied to 21,814 consumers in
the Tamar zone. An improvement programme to optimise treatment at the
Tamar works and to improve customer ag ent training is due f or complet ion
in December 2017.
There are a number of legally-binding programmes of work in place to
improve tast e and odour f or consumers in the W estern region. At Tottif ord
32
Western region
works (SW T) granular activated carbon (GAC) treatment is to be inst alled
and addit ional treatment is also planned at f our other works: Crownhill ,
College, Northcombe and Tamar (SW T). These are all due to be completed
by December 2019 benef iting over 780,00 consumers.
W essex W ater has recent ly completed a scheme to convert exist ing
sand/GAC f ilters to sand f ilters, construct manganese f ilters and p rovide
dedicated granular activated carbon f ilter s (GAC) to mitigate for pesticides
and taste and odour at their Sutton Bingham works.
A f urther taste and odour scheme in Por lock is due f or completion in 2017
where consumer s had been exper iencing earthy/m ust y tastes in their
drinking water supplies due to the presence of geosmin and methyl
isoborneol. As part of this scheme the Porlock works and Moorbrake
ser vice reser voir have been abandoned and the company is optimising
point of use treatment and install ing robust backup arrangem ents f or six
concessionar y supplies (see Annex 4).
Aluminium
Alum inium can occur naturally in some water sources. Also, aluminium based water treatment chemicals may be used at surf ace wat er works to
aid the process of f iltratio n.
In 2015, a total of 4,739 samples were tested f or aluminium in the W estern
region. Just t wo test s exceeded the st andard (1 BRL, 1 W SX); neither
related to process control at the works.
In October a consumer’s tap sample in the Clif ton, Horf ield, Redla nd and
Kingsdown zone was collected f rom a property and f ound to contain
669µg/l of aluminium and 69µg/l of manganese . This was concluded to be
as a result of mains disturbance in a distribut ion system known to be
aff ected by sediment in cast iron mains. T he company has prioritised its
f lushing program me in the area.
W essex W ater’s Investigations of a f ailur e in Lulworth zone, in October ,
determined it was caused by a water condit ioning unit plumbed into the
cold water supply. The customer was ser ved with a section 75 order and
the unit was replaced by the company. All subsequent samples have been
satisf actor y.
Chlorine
Chlorine is widely used as bleach and has a long histor y of use in
circumstances where the maintenance of good hygiene is essential, f or
33
Drinking water 2015
example, f ood preparation, swimming pools and water supplies . In the UK
levels of residual chlorine in tap water ar e ver y low, t ypically 0.1 – 0.5mg/l
and rarely exceeds 1.0mg/l in water drawn f rom taps in prem ises . This
compares ver y f avourably to the W orld Health Organisation ( W HO) healthrelated guide value of 5mg/l.
W ater companies ar e required to measur e residual chlor ine whenever
samples are collected f or microbiological analysis . Any abnor mal change
in the level of residual chlor ine in a particular s upply must be invest igated.
The Inspectorate checks the action taken by companies in relat ion to any
chlorine result above 2mg/l at treatment works, at service reservoirs or in
zones. Across the region in 2015, there were t wo of these abnormal
results. The causes and act ions taken by the companies are described
below.
In December Brist ol W ater recorded a maximum level of total chlorine at
Barrow works of 2.1mg/l. This sample was taken when the works was
starting up and the trends show the residual quickly returned to the set point of 1.0mg/l as the f low came back up. The company has conf irmed
there were no contacts associated wit h the increased chlorine.
Additionally a ver y high f ree chlorine level of 11.8mg/l was reported at a
sample in Bristol W ater’s Ch edder, W edmore, Brent Knoll and Burnham on-Sea zone in December. This result has been conf irmed as a data input
error and should have been entered as 0. 63 mg/l. In this instance the
temperature was ent ered in the f ree chlorine f ield. The company has
established an error in the data integrit y checking process . The process
has been impr oved t o avoid a reoccurrence.
In addition to invest igating any abnormal change in the level of residual
chlorine, water companies must also investigate and address any sit uatio n
where the level of residual chlorine is not acceptable to consumers.
Companies theref ore have in place protocols f or receiving, assessing and
recording contacts f rom consumers repor ting chlor ine-related tastes or
odours in tap water. Figure 14 maps the chlorine taste and odour
consumer contact rat e per 1 ,000 population f or all zones in the W estern
region dur ing 2015.
34
Western region
Figure 14: Map illustrating rates of chlorine-related consumer
contact s to w ater companies per 1,000 population
From Fig ure 14 it can be seen that consumers in W essex W ater’s Ashf ord
Stoney zone (bet ween Minehead and Glastonbur y) exhibit a r elat ively high
rate of reporting chlorine-related tastes and odours (> 2.5 per 1,000
populat ion) and this is well in excess of the industr y averag e of 0.2 per
1,000 populat ion. This inf ormation will to be taken into account during the
Inspectorat e’s f or ward programme of technical audit in the region.
Copper
Copper is used ext ensively in pipes and f ittings. Copper occurs in dr inking
water when used wit hin building wat er systems. In general, water supplies
in the UK are not aggressive towards copper, but there can be occasional
problems with newly installed plum bing.
A level of 2.23mg/l copper was reported in a sample f rom a public building
(villag e hall) in the Dotton zone in February. South W est W ater carried out
a f ittings inspection that conf irmed sat isf actory copper plumbing
arrangements and advised to per iodically f lush internal plumbing and
check earth straps. All f ollow -up samples, including repeat samples f rom
the original tap , wer e satisf actor y.
35
Drinking water 2015
Fluoride
Traces of f luoride occur naturally in many water sources, particularly in
groundwaters. In this region, naturally occurring f luoride is found in water
drawn f rom the great Oolite lim eston e in t he area of North East Somerset
and W est W iltshire (particularly ar ound Lacock). Consumers can obtain
specif ic inf ormation on the level of f luoride in the drinking water supply to
their home or workplace f rom their water company. Fluoride is not remov ed
by conventional water treatment.
In 2015, all 1,270 tests f or f luoride taken across the region met the
regulator y standard ( 1.5mg/l).
On 1 April 2013, the Secretar y of State f or Health became responsible f or
exist ing f luoridation schemes via Public Hea lth England, and local
author ities became responsible f or proposing and carrying out consultation
on new schemes and extensions to existing schemes.
There are no f luoridation schemes in the W estern region.
Lead
Lead in tap water t ypically ar ises in pr emi ses where the pipes and br ass
f ittings have not been ref urbished since t he 1970s when the use of lead in
contact with dr inking water was banned. The other reason why lead may
be f ound in tap water is t he illegal use of lead- based solder f or making
joints on copper pipes.
In addition to the ban, the standar d has been pr ogressively t ightened f rom
50µg/l in 1990 to 25 µg/l in 2004 and since the end of 2013 has stood at
10µg/l. Dur ing this time water companies have assessed the r isk of lead
being present in tap water at the point of use and , wher e necessar y,
installed additional water treatment (generally phosphate dosing or pH
correction) to minimise the propensit y of lead to leach out of pipes and
f ittings within consumers’ premises.
Since the only perm anent long-term solution to the issue of lead in tap
water is the removal of lead pipes and f ittings, water companies have been
engaged in a range of other activit ies to identif y where specif ic act ion
plans f or lead removal are required, f or exam ple , in social ho using or
schools. If a lead f ailure occurs in a public building then water companies
and local aut horit ies are able to use their powers to require the owner to
remedy the problem; however, in relat ion to private pr opert y, water
companies and local authorit ies can only give advice, they cannot compel
homeowners to replace lead pipes or f ittings.
Figure 15 shows the position of the W estern region in relation to the
industr y as a whole and illustrates that regional compliance with the lead
36
Western region
standard is now in l ine with the industr y f igure. In previous years, f rom
2009 to 2014, the region had been slightly outperf orming the industr y as a
whole.
Figure 15: Percentage of tests meeting the standard of 10µg/l for lead
betw een 2006 and 2015
In 2015, companies in the W estern region reported seven (1 BRL, 6 W SX)
f ailures of the standard of 10µg/l out of a total of 1,350 tests.
All of these f ailures were in zones where the water supply is t reated to
reduce the risk f rom lead and none occur red in a sample collected f rom a
public building. In all cases, advice was provided to consumer s and the
source of lead was identif ied through inspec tion. W here possible the
companies replaced their part of the ser vice pipe or the whole service
pipe. In one instance , in W essex W ater ’s Hampton Down zone in Apr il, the
company did not maintain their treatment due to a change in supplier.
Companies are expected to ensur e that water treatment is a lways
maintained and opt imised.
Methylisoborneol
Methylisoborneol is a natural substance produ ced by the growt h of algae,
normally in surf ace waters which gives r ise to a characterist ic ‘earthy’ or
‘must y’ taste or odour. It is detected by the method f or assessing taste and
odour.
37
Drinking water 2015
In 2015, South W est W ater investigated detection s of taste and odour in
samples taken in f our of South W est W ater’s zones (St ithians, Restormel,
Prewley and Northcombe) during August and September.
These exceedances all occurred af ter a period of sudden heavy rain
caused an unprecedented rise in raw wat er concentrations o f
methylisoborneol – over ten times the pr evious maximum level. Temporary
treatment (powdered activated carbon) was inst alled alt hough it took a
number of weeks f or levels to be reduced to below taste thresholds. This
temporar y treatment will remain on site until the permanent installat ion of
treatment is complet ed. There are Not ices in place at these sites (see the
Aesthet ic parameter s: Taste and odour section).
Nickel
Nickel may be present in coatings on modern tap f ittings. In 2015, a total
of 3,702 tests were carried out f or nickel and all but six ( 2 BRL, 4 W SX)
met the standard (20 µg/l).
Bristol W ater reported two f ailur es f or nickel in 2015. The f irst was in
March in the W hitchurch, Hengrove, Knowle and K nowle Park zone, and
the second in the Long As hton, Failand, Bishopsworth and Dundr y zone in
May. Both wer e f ound to be due to a non - W RAS approved taps in the
customer property. The customers were advised and replaced the taps.
Sim ilarly f our nickel f ailures were ident if ied in the W essex W ater area, in
the f ollowing zones, Porlock (Februar y), Clarendon (Apr il) and Bowden
(August and October ). These f ailures were all attributed to the customer
taps. The consumers were advised to ensure that standing water is f lushed
bef ore drawing water f or drinking . In the case of the f ailure at Bowden, this
f ailure was at a school. Com panies ar e reminded that where a public
building is involved, they must require remediat ion by the building owner.
In this instance a section 75 Not ice requiring the tap to be changed wa s
ser ved.
Nitrate and nitrite
Nitrate occurs natur ally in all source wat ers due to the decay of vegetable
material in soil. Nitrogenous f ertilisers used on arable f armland are a
signif icant source of nitrate in groundwat er. Rainf all washes nitrate f rom
the soil into lakes, river s and streams. Nitrate levels can be r educed by
water treatment or by blending with anot her, low nitrat e, wat er source.
In 2015, all tests f or nitrate met the standard (50mg/l).
38
Western region
A Not ice is in place t o install treatment at Chold erton works to remove
nitrate by the end of March 2020 benef iting 2,100 consumers ( see
Annex 4).
W essex W ater are constructing an integr ated grid system and carrying out
catchment managem ent to f acilitate blending as a solut ion to nitrate risks
at seven s ites (Bulbr idge; Chirton; Dunkerton; Fonthill Bishop; Hooke;
Sturminster Marshall; and W ylye). The catchment management work was
completed in March 2015 with the grid system to allow blending in place by
2018. Once complete this improvement scheme will ben ef it approximately
22,000 customers.
Nitr ite may be f ormed when chloram ine is used as the residual disinf ectant
to maintain the m icr obiological qualit y in the distr ibut ion net work. The
f ormation of nitrite is controlled by caref ul opt imisation of the
chloramination process. Bournemouth W ater and W essex W ater have
arrangements where W essex W ater can receive bulk supplies of
chloraminated water f rom Bournemout h W ater . Nitr ite can also f orm in
samples of water, af ter collect ion and bef ore analysis, especially if the
sample is not kept cool.
In 2015, all 1,701 tests carried out across the region f or nitrit e met the
standard.
Pesticides and related products
This group of substances, generically called pesticides, includes many
organic chemicals ranging from wee d killers, to insecticides and
f ungicides. W ater sources may cont ain traces of pesticide residues as a
result of agricultur al use (pest control on crops) and non -agricultural use
(herbicides f or weed control on highways, railways etc.). W ater companies
are required to assess the risk to drinking water supplies of pesticide use
in source water catchments and then test f or those that might be present.
Companies have taken raw water monitor ing into account when
document ing potent ial and actual pesticide hazard s through t heir
Regulation 27 risk assessments. W hen pesticides are f irst detected, water
companies will enhance the monitor ing of raw water and not ify the
Environment Agency to f acilitate appropriate action in the cat chment to
saf eguard drinking water qua lit y.
Table 16 illustrates t he potential pesticide risk in the region and compares
it to the actual pesticide risk in 2015. Out of a total of 372 raw water
monitor ing points, 188 were subjected to risk -based monitor ing f or
pesticides and the risk was ver if ied by posit ive detection of pesticides at
only 46 abstraction points.
39
Drinking water 2015
Table 16: Raw w ater monitoring point s at risk from pestici des in 2015
Numb e r of r aw
w at er m onit or ing
point s
Raw w ate r
monit o ring po int s
monit o red fo r
pe sti ci de ri sk
Numb e r of r aw w ate r
monit o ring po int s
w her e p e sti ci de ri sk
v er ifi ed b y
monit o ring
B our n em out h
W ater
24
11
2
Br is t o l W ater
39
11
3
Comp an y
Ch o ld er to n a n d
Dis tr ic t W ater
S ou th W es t
W ater
V eo l i a W ater
Pr oj ec ts Lt d
2
0
0
63
56
34
3
3
1
W es s ex W ater
24 1
10 7
6
Reg ion a l tot a l
37 2
18 8
46
Indu st r y tot a l
2, 5 53
1, 5 06
22 9
Data are for raw water monitoring points in the region in 2015. Verification of risk is based on at
least one sample containing pesticide above the limit of detection. SSE Water does not operate
abstraction points in the region.
The outcome of pesticide risk management by companies in t he region was
that there wer e no f ailures of the pesticide standar ds in treated water in
2015.
Metaldehyde
In 2015 Br istol water completed its pr ogramme of work f or metaldehyd e in
the Chew Valley. Ext ensive work with the local f arming communit y, who
have been ver y r eceptive to the init iative, has minimised the amount of
metaldehyde (the act ive ingredient in som e slug pellets), f rom getting into
f arm drains and subsequently to s treams and the lake itself . The
programme included one -to-one f arm visit s, calibrat ion of slug pelleter
machiner y and a general awareness campaign. As a result, levels of
metaldehyde in the Chew Valley Lake have been below the st andard of
0.1ug/l since 201 2 and thus the company has assessed th at the f urther
treatment at Stowey works is no longer required as the inf ormation
gathered f rom monitoring and trend prediction indicates a low risk to raw
water qualit y.
A sim ilar programme of work in Brist ol W ater’s Littleton and Purton
catchments continues.
40
Western region
Sim ilar success with catchment control has been reported in t h e W essex
W ater area f eeding Dur leigh works. Actions taken here include; awar eness
raising, keeping f armers inf ormed of the latest water qualit y data, advising
on best pesticide practice, joint f arm visits bet ween the Environment
Agency and W essex W ater identif ying par ticular at risk f ields/f arms.
Additionally W essex W ater f unded product substitut ion in the area whereby
all f armers in the cat chment are eligible for support f or 80% of the cost of
switching f rom metaldehyde to f erric phosphate-based molluscicides.
Radioactivity
Gross alpha/gross beta/ total indicati ve dose
Radioactivit y in raw water can occur naturally in the environment or f rom a
specif ic point source emission. W ater companies are requir ed to screen f or
radionuclides that emit either alpha or beta particles. If such screening
exceeds guide values (Gross alpha 0.1Bq/l, Gross beta 1.0Bq/l) then f uller
analysis f or specif ic radionuclides is carried out to determ ine t he origin.
Under these circumstances the total indicative dose (TID) must be
calculated. TID is a measure of the eff ective dose of radiat ion through
consumpt ion of the water and no f urther action is required if the guide
value of 0.1mSv/ year is not exceeded .
W here screening and other inf ormation has shown there to be no risk
relat ing to radioact ivit y in a specif ic wat er supply, companies can apply f or
and have been granted, an exem ption f rom f urther radioactivit y monitor ing
(known as a waiver) by the Inspectorate. In 2015, no new or replacement
waivers were granted.
Tritium
Monitor ing f or tritium is necessar y only where a source of tritium is present
within the catchment and it cannot be shown on the basis of other
sur veillance program mes or investigations that the level of tritium is well
below its parametr ic indicator value of 100Bq/l. In 2015 , 183 t ests (36
BRL, 99 SBW , 4 SSE, 32 SW T, 12 W SX) f or tritium were car ried out in the
W estern region and all results were below the scr eening value of 100Bq/l.
Three companies in t his region have established by r isk assessment that
monitor ing f or tritium is not required (CHO, SW T, VW P) , however , Sout h
W est W ater submitted some oper ational samples in err or as they were
granted a waiver in 2014, subject to review af ter f ive years or if
circumstances change, permitting them to cease sending test results f or
tritium to the Inspect orate.
41
Drinking water 2015
Monitor ing waivers t ime expir e af ter f ive years and the Inspectorate has
been in discussion with companies to ensure they are now car rying out
monitor ing in tho se situat ions wher e a waiver has not been renewed.
The EU Council Directive made under the Euratom Treaty came into ef f ect
in October 2013. The Dir ective sets out t he requirements f or the protect ion
of the health of the general public with regard to radioactive substances in
drinking water. In England the Inspectorate has been working closely wit h
Def ra to ensure that the necessar y changes are made to the 2016 dr inking
water qualit y regulations. The pri ncipal change introduces new
requirements f or radioactive paramet ers, in part icular the indicator
parameter radon, with its own monitoring requirements. The ot her
requirements already being in place.
The Inspectorate commissioned a project to understand th e implications of
the EC’s proposals r elat ing to radon in dr inking water in the UK and the
report may be f ound on the Inspectorate’s website. In May 2015, the
Inspectorat e published the requirement for companies to carry out risk
assessments f or radon in a ll of their catchments . Also to begin regulator y
monitor ing f or radon f rom 1 Januar y 2016 where the r isk is considered to
be moderate or high , or until risk assessment shows there to be no or low
risk and monitoring can cease.
Maintaining water quality in distribution
Elevated levels of iron or manganese ar e objectionable to consumers
because the water may appear turbid or discoloured due to unsightly
deposits and may also stain laundr y and water f ittings. Since 2004 the
Inspectorat e has been monitor ing t he progress of companies’ distr ibut ion
maintenance work, using an index made up of three parameters (turbidit y,
iron and manganese). Figure 17 shows t he long -term improvements in the
W estern region. In 2015, there was f urther improvement across the region,
to 99.94% over all, which exceeds the industry average of 99.91%.
42
Western region
Figure 17: Percentage of tests meeting the standards for t urbidit y,
iron and manganese
Note: SSE W ater only began supplying water in 2008. They have achieved 100% in each year
since.
Veolia W ater Projects only began supplying water to Tidworth in 2009. They have achieved 100%
in each year since.
C h o l d e r t o n a n d D i s t r i c t W a t e r h a v e a c h i e v e d 1 0 0 % i n e a c h y e a r e xc e p t 2 0 0 2 ( 9 5 . 8 3 % ) , 2 0 0 3
(97.62%) and 2004 (97.22%).
Discolourat ion of tap water of ten prompts consumers to contact their wat er
company. The number of people contact ing water companies about
discoloured water is reported annually to the Inspector ate in accordance
with Inf ormation Letter 1/2006. Looking at the trend since 2008, it can be
seen f rom Figure 18 that across the industry, the numbers of consumers
contact ing their water company to complain about discoloured water has
f allen f rom 70,648 to 44,141 in 2015. Between 2014 and 2015 in the
W estern region there was a small decrea se in contacts f or discolouration,
with the f igure now standing at 6,100, down f rom 7,171 in 2014. Overall
the region accounts f or 14% of all consumer contacts f or discolouration
across England and W ales.
43
Drinking water 2015
Figure 18: Total contacts for discolouration 2008–2015
In Drinking water 2014 , the Inspectorate asked companies to review
consumer contact data on a cont inuous basis to identif y zones with
persistent problems that require remediat ion, irrespective of whether the
zone has been the subject of improv ement works in the past. In 2015, the
Inspectorat e carried out the exercise to identif y these zones starting with
where the level of consumer contacts had been above the industry level f or
the three preceding years. Discolouration of tap water of ten prompt s
consumers to contact their water company indicating a persist ing problem
f or consumers. Further work then identif ied six companies in England
where such zones existed, but wher e no legal instruments were in place.
Legal instruments describe the planned drinking water qualit y
improvements of companies where progress to rectif y the problem can be
monitored against set objectives. The Inspectorate met with t he companies
to understand what plans existed in these areas to reduce consumer
contacts f or discolou ration, distribut ion compliance f ailures and water
qualit y events. Such plans would be expected to include, treat ment works
upgrades, reser voir cleaning and carr ying out operational measures (such
as f lushing) within zones to help improve distribut ion wate r qualit y.
Af ter reviewing the company plans, customer contact data, compliance
f ailures and distribut ion water qualit y event inf ormation the Inspectorate
assessed these plans to see if they aligned with the areas of concern and
were appropr iately t argeted to their own perf ormance targets. W here
necessar y, the Inspectorate issued new legal instruments to formalise
these operational plans ensuring deliver y of the required improvements f or
the benef it of consumers.
44
Western region
From the review, o ne company was ident if ied as being in the South W est
region (SW T). South W est W ater has an operat ional f lushing programme
which will see mains f lushed in 12 zones identif ied as having high
discoloration contact rates in this exercise. In order to ensur e the f ull
deliver y of these programmes, the Inspectorate has initiat ed enf orcement
action in the f orm of zonal Regulat ion 28 Notices in the area shown in
Figure 19. The Regulat ion 28 Not ice also includes steps f or the company
to investigate and develop a longer term strategy which wi ll help direct
f uture investment to reduce the discolour ation r isk in these zones.
Figure 19: Zones w here Notices have been served to address
discolouration
In 2015, across the whole of the W estern region, out of a total of 15,660
tests f or the f our para meters (iron, mang anese, turbidit y and
benzo( a)pyrene) ther e were 15 f ailures (ir on 13; manganese 2). The
Inspectorat e expects that the location and circumstances of the 15 f ailures
reported by the com panies will have been taken into account during the
relevant risk assessments and Distr ibut ion, Operation and Maintenance
Strategies. The details of where f ailures occurred ar e descr ibed below.

W essex W ater – two f ailures f or iron. One of these in the Maundown
Central zone was f ound to be due to corr osion of t he propert y
ser vice pipe. The company has replaced the communication pipe and
advised the customer accordingly. The second of these f ailur es, in
the Hampton Down zone, was considered due to mains deposits in
the local area and f lushing was carr ied out.
45
Drinking water 2015

South W est W ater – f ive f ailures f or iron, one f ailur e f or manganese.
These f ailures (one of which was considered due to illegal hydr ant
use disturbing mains deposits) wer e in the Exeter/ Okehampton/
Tiverton area. The r emaining f ailur es were considered due to mains
deposits in the local area and f lushing was carried out. Five of the
f ailures were in zones where the Inspect orate has ser ved Notices f or
discolourat ion.

Bristol W ater – six f ailures f or iron, one f ailure f or manganese. The
f irst was recorded in the Yate, Coalpit Heath and W armley zone in
March ser ved by a cast iron main which t he company has since
abandoned and replaced. The remaining f ailures were considered
due to a build-up of iron mains deposits in the distribution system.
The company will conti nue to use a Distribution Operat ion and
Maintenance Strategy to determine where f lushing, mains
replacement or f urther investment is req uired.
In all cases the Inspectorate will also take this inf ormation, the consumer
contact rates and the eff ectiveness of company strategies int o account
during its risk assessment of companies and, where appropr iate, take
enf orcement action.
Annex 4 details the legally- binding programmes of distribut ion
maintenance work scheduled f or completion bet ween now and 2020 to
address ongoing dist ribut ion quality problems in the region.
46
Western region
Chapter 5: Drinking water quality events
Chapt er 5

Explains how events are classif ied.

Provides summary f igures of the number and t ype of events.

Illustrates industry- wide lear ning point s f rom case studies.
W ater qualit y events are classif ied into f ive broad categories based on the
initial company repor t. The categories are:
Not significant: no f urther inf ormation required by an inspect or to assess
the event.
Minor: it is unlikely t hat f urther inf ormation would be requir ed by an
inspector to assess t he event .
Significant: a f ull company report is usually required to enable an
inspector to assess t he event .
Serious: in addition to a f ull company report, the assessment may involve
more than one inspector and site visits in the investigation.
Major: in addit ion to a f ull company r eport, will require an investigation led
by senior inspectors involving extensive inf ormation gathering and usually
site visits.
In 2015, companies in the W estern region notif ied the Inspect orate of
72 events. Table 20 shows how these events were classif ied.
Table 20: Water qualit y events in the region in 2015
Nat ur e of ev e nt
A ir i n wa t er
Ch em ic a l
Dis c o l our e d wa t er
In a de q ua te t r e atm en t
Los s of s u p pl i es / p o or pr es s ur e
M ic ro b i ol o g ic a l
T as te /O d o ur
He a lt h c o nc e r n
P ub l ic c o nc er n
O th er
Reg ion ov er al l
Eng l and an d W al e s
Ri sk as s es sm ent cat ego r y ( DW I)
M inor*
Si gnif i ca nt
S er iou s * *
20 1 4
20 1 5
20 1 4
20 1 5
20 1 4
20 1 5
1
2
3
1
2
1
6
3
1
9
2
6
6
7
2
6
5
9
6
1
2
8
2
5
1
6
9
12
4
13
3
2
10
1
32
38
53
33
1
28 1
32 2
21 8
22 3
12
10
* Mi n o r c a t e g o r y n u m b e r s i n c l u d e a l l n o t s i g n i f i c a n t a n d m i n o r e ve n t s
* * S e r i o u s c a t e g o r y n u m b e r s i n c l u d e a l l s e r i o u s a n d m a j o r e ve n t s
47
Drinking water 2015
A summar y of the nature, cause and dur ation of each event categorised as
signif icant, serious or major along wit h details of the Inspect orate ’s
f indings are set out in Annex 3. Most events were of relat ively short
duration and the company took appropriate acti on to inf orm and saf eguard
consumers and other stakeholders. A com parison of 2014 events with
those of 2015 shows an overall decrease in the numbers of signif icant,
serious and major events, although an increase in those relating to public
concern. The one seriou s event in the region is descr ibed below.
The importance of aw areness and responsibilit y tow ards safe w ater of
all those w ho w ork on w ater company sites
In September , a routine compliance sample, taken f rom a common outlet of
a two compartment service res er voir, reported one conf irmed E.coli and
>100 colif orms per 100ml.
In response the com pany initiat ed an investigation taking a number of
resamples f rom the service reser voir, supplying assets and the
downstream net work; a sample audit within the laborato r y to ensure the
testing condit ions of the sample wer e corr ect and an external inspect ion of
the ser vice reser voir . This inspection discovered a possible r oute of
ingress into the chamber of the second compartment through an unsealed
ext ernal cable duct si tuated underneat h some paving slabs. Af ter opening
the inner hatch it was conf irmed that this cable duct was f ound to have
direct access to the treated wat er (see Figure 21). No external signs of
ingress were f ound around the chambers of the f irst compartm ent.
Figure 21: Rout e of ingress
48
Western region
The company isolated the aff ected compartment in preparation f or an
internal inspect ion. The f irst compartment remained in supply and as a
result, the company issued a boil water notice and provided bottled water
to customers supplied by the ser vice reservoir unt il the invest igation was
completed.
W hile the internal inspection f ound no f urther signs of ingress the remains
of two mice were discovered. The company completed the repairs to seal
the route of ingress through t he cable duct.
Further samples wer e taken across the supplying area and f ollowing t wo
days of satisf actory results the boil water notice was lif ted. Following the
return to ser vice of the second compartment the company completed a
similar internal inspecti on of the f irst compartment which was f ound to be
satisf actor y.
Following a previous event, the company had implem ented reg ular integrit y
inspect ions at its ser vice reser voirs , but t his had not been pr ioritised f or
this site and consequently t he ingress wa s not ident if ied. In this event, the
company were unaware of work on site or that it had af f ected water
qualit y. This illustrat es the need f or companies to ensure communicat ion
routes are in place so that those responsible f or wat er qualit y are notif ied
by those responsible f or initiat ing work on site. Had this been carried out,
a risk assessment would have resulted in a prior itised inspect ion and this
would have avoided the need to respond to a sample f ailure causing
considerable inconvenience to consum ers where a boil water notice was
necessar y. The company f ollowing this event init iated a new qualit y
scheme f or W ater Supply. ‘Think Qualit y, Be W ater Smart’ to ensure all
those who visit and work on their site ar e aware of their responsibilit y
towards saf e wat er. This builds upon the successf ul and similar initiative
by Northumbr ian W ater the year bef ore which other companies might f ind
usef ul.
Ser vice reser voir visits are inf requent and while many companies do
conduct secur it y checks and complete sit e maint enance the Inspectorate
recommends that companies implement inte grity inspect ions at a
f requency determined by the water saf ety plan f or each asset. If the
company had continued to conduct its integrity checks at this service
reser voir then this event coul d have been avoided.
The f ollowing examples are included in t his report because of the industr y wide learning points.
49
Drinking water 2015
Failure of disinfection control – w eakness of asset design and
function
During the year ther e were t wo events at Sweet loves works concerning
improperly disinf ected water as a result of the loss of pH cont rol in the
disinf ection treatment stage. Sweetloves works is sit uated nor th of Bolton
and supplies just short of 80,000 propert ies. The treatment consists of
coagulat ion, clar if ication an d pr imar y and secondar y f iltration with pH
adjustment at sever al points bef ore disinf ection. The control of pH is
critical to the process so when in both cases, control was lost due to the
f ailure of a sample pump to the pH meter , the resultant high pH (>p H10)
interf ered with the f ormation of hypochlor ous acid f or eff ective disinf ection.
For the f irst event the company decided against isolation of the contact
tank due to the length of time to operate the isolat ion valves and risk of
interrupting supply t o customers. The company also de cided against the
issue of boil water a dvice due to the timescale involved in distribut ing
notices and addit ionally that the raw wat er qualit y was within normal
ranges and not indicating any signif icant challenge to the wor ks.
For the second event the company were slow to recognise the same
scenar io, but once r ealised, actively wor ked to restrict any f urther
improperly disinf ected water ent ering supply . The company again decided
that boil water advice was not required. However , due to the length of time
it took to regain cont rol of the treatment process , alternative supplies were
insuff icient. The com pany latterly decided to release the im properly
disinf ected water, in associat ion with a boil wat er advice , provided the pH
did n ot exceed 9.5.
Public Health England, as part of their role, will provide advice and
inf ormation to the public, prof essionals and government on health
protection issues, based on scientif ic and healt h protect ion expertise. The
company consulted with PHE o n both occasions and they supported the
decisions f or which the company remain responsible.
This event pr ovides a f urther example of companies f ailing to prevent
inadequately treated and disinf ected wat er entering supply f rom works and
f ailing to control o perational r isks in the light of previous events and when
the company is clear that the control is dependent upon cr itical equipment.
It is questionable when the company strat egy considers it acceptable not
to put in robust maintenance f or something as bas ic as sampling pumps
compared to the senior decision and business risk necessar y to recover
f rom events of this size when considering a boil not ice. Furthermore, why
has the company not considered the design of the contact tank which in its
current state could only be isolated and not discharge any improperly
treated wat er to waste? Even when the situation results in the inevitable
50
Western region
and a boil not ice is called f or, why is ther e not eff ective management and
an eff ective public health protect ion?
Senior managers must be awar e and be responsible f or water qualit y and
this must include all aspects of company operat ions. There m ust be clear
understanding at the most senior level that risks are identif ied, works and
assets work within predesigned lim its, the techno log y is suitable and
robust, and redundancy is built in to crit ical steps; control measures are in
place and robust, and those who work in or with the company are
competent to carr y out the f unctions and duties of the company. Senior
managers should expect that the Inspect orate will continue to ident if y
those companies who present the greatest risk to be a f ocus of attention.
W hile there was a catalogue of errors in both events, the greatest
weakness was the design. In addit ion, there was the inconsistent a pproach
to issuing boil water advice, which was symptomatic of policy. The
Inspectorat e expects companies to have appropr iate design of treatment
assets and robust public health policies.
Issue of a do not drink notice to 17 properties
In May to June, 17 properties in the village of Stoke Goldington,
Northamptonshire were issued with a do not drink not ice when the
company detected polycyclic ar omatic hydrocarbons (PAH) in the water
af ter planned cleaning. PAHs are pr esent in coal tar, a technique widely
used bef ore 1970 to line the inside of iron pipes. W hen the lining degrades
or is disturbed by cleaning, PAHs can be released into the water result ing
in an unpleasant tast e of ten described as similar to white spir it. The
Inspectorat e noted t hat this outcom e was the result of a consumer
complaint dating back three years when she complained her water was the
colour of teabags, lef t a rusty looking residue in the sink and she could not
use the water supply f or drinking, cooking, laundr y or washing. The
consumer f inally resorted to contact ing the Inspectorate in August 2014
who took up her case on her behalf .
During the period June 2014 – June 2015, the company tried: mains
f lushing, air scouring, partial mains replacement, ice pigging and
eventually conducted a complete mains r eplacement of old cast iron main,
which f inally solved t he problems in the local net work. Prior to complete
mains replacement of a f urther 1.4km section in addit ion to the initial
replacement of 900 meters, the company were still detect in g high levels of
iron to which the company decided to use ice pigging . This is a relat ively
new technique which is becoming more widely used since it simply uses
crushed ice pushed t hrough the pipe as an abrasive mater ial for cleaning.
It was this exercise which led to the release of PAHs f rom a previously
unknown coal tar lining . The cleaning was unsuccessf ul due to a blockage
51
Drinking water 2015
in the main which had restricted the eff ectiveness and the f ull mains
replacement f inally r esolved the matter in June.
There are any number of criticisms that could be levelled at the company
in this event, not least was the f act that it was unnecessarily protracted;
the remedial techniques wer e poor ly chosen, planned and inappropr iate
given the u ncertaint ies of mains materials and potential linings present in
an old cast iron main in the area . It remains, however, that this event may
well have been avoidable had a risk analysis appropr iate f or ice pigging
been ef f ective. This technique has result ed in a number of events in recent
years and close scrutiny of these events of ten uncovers uncer taint ies of
the company over their own net works and of the applicat ion of the method.
Companies are reminded to ensure they are f amiliar wit h the technique
and to ensure it is appropr iate f or the ta sk in hand bef ore use. In this
instance had the company elected to replace the whole main rather than
half of it, the event would never have happened and while it is impossible
to understand the exact reasons f or the decision at the time, a long -term
risk assessment would have ident if ied the removal of all the degraded iron
main as this would have elim inated this event f rom ever happening again
in the f uture.
Fundamentally, however, this was the f ailure of the company to their
consumers: The consumer who h ad been complaining f or three years;
those consumers who complained of unusual tastes ; and the signif icant
inconvenience and distress to some of the consumers ser ved, whose
businesses and social plans were severely disrupted when the event
occurred.
Loss of primar y disinfection
In the late hours of 1 October the main chlor ine dosing syst em at Frankley
works f ailed. Chlorine is the most commonly used disinf ectant f or water
and is used to remove any remaining micr obes af ter treatment. An
important process su ch as this is expected to have a secondar y syst em in
place which starts automatically in the event of the main chlorine dosing
system being lost. Such a system exists in Frankley works , but in this case
the backup system f ailed to operate as expected. As a result the plant did
not dose chlorine f or a period of about six hours. Frankley works supplies
around 1.5 million people in Birmingham and parts of the W est Midlands. A
critical treatment works supplying water t o the UK’s second largest city,
the consequence of a loss of disinf ection and possib ly the supply, at the
ver y least would cause signif icant disrupt ion to the consumers and the
cit y.
The company carr ied out an invest igation and determ ined the computer
controller of the main chlorine dosing system had f ailed. The system was
52
Western region
such that this same controller operated the back -up system and provided
inf ormation to the control centre. The event resulted f rom the single
operat ional control dependency of both the primar y and back -up
disinf ection. Consequent ially when the control system f ailed, the works
f ailed and the company were unaware of the status of dosing. The
Inspectorat e attended the site in October and issued a Provisional
Enf orcement Order in relat ion to a f ailure to adhere to the condit ions of an
exist ing Not ice at the works. This is a very unusual step f or the
Inspectorat e to take and ref lects the ser ious concerns to the f undamental
principle of having separate systems on critical processes. The Order
required the company to reassess the design a nd control of the works to
ensure that chlorinat ion systems did not f ail in this way. It also stipulat ed
that suff icient trained staff were available to run the plant, particular ly
outside normal working hours. The company has redesigned t he system
appropr iately complying wit h the P rovisional Enf orcement Order.
The Inspectorate reminds senior managers in the industr y that they are
responsible f or ensuring systems are in place and ar e robust t o prevent
inadequately treated and disinf ected wat er entering sup ply f rom works, a
point made repeatedly this year and over the 25 years it has been a
requirement. This pr inciple, arguably of resilience f or companies, is not
solely about interconnectivit y, but also retaining f ocus on the f irst
principles of operating tr eatment works which are too crit ical to f ail.
Auto shut-dow n arrangements
As a precautionar y measure to ensure water is appropr iately treated and
disinf ected bef ore leaving works, a saf eguarding syst em was installed to
prevent a works f rom being started w hen turbidit y increa ses above the
standard of 1NTU. This was in response to an event at Matts Hill works in
2008 where the com pany was prosecuted in 2010 f or permitting turbid
water to enter supply by repeat edly over riding f ail saf e controls. In July
2014 the Inspect orat e received inf ormation concerning the abilit y to evade
this new system by bypassing on-line monitors at works. Doing so would
permit a works to start improper ly where other wise an alarm would sound
in response to the pr esence of turbidit y or chlor ine pr oblems saf eguarding
untreated water ent ering supplies.
A series of 12 investigatory site audits were carried out to investigate this
inf ormation and f ollowing detailed testing it was conf irmed that it was
possible to bypass on -line monitors without alarms being raised and avoid
sites being auto matically shut down. Investigations not ed the instrument
design permitted nominated operat ors to start certain sites without causing
a shutdown, however, the knowledge of the method had become commonly
known and subsequently used inappropr iately through the wider area of
53
Drinking water 2015
the company. By allowing this pract ice to continue, local management and
theref ore the company had f ailed to put adequate measures in place to
prevent rout ine abuse of the ver y system desi gned to prevent
inappropr iate practice and consequent ly t he potential increased risk to its
customers.
The monitor alarm system has since been updat ed and the company
initiated the need f or managers’ inter vent ion when sites sound an alarm
indicating water qualit y is outside the set parameters. Any attempted
bypassing of on -line monitors is now clearly visible on the company’s
SCADA system. Following the discover y by the Inspectorate, the company
has worked closely with the on - line monitors’ manuf acturer, to determine if
the monitors could be bypassed in other ways and to ensure f uture
untoward tamper ing is prevented.
This ser ves to rem ind companies that when expensive on-line monitor ing
systems are order ed and installed, appr opriate verif icat ion should be
carried out as part of the commissioning stage where all relevant persons
within the company are involved, including process and water qualit y
scientists. It is disappointing to state that while such occurrences are ver y
rare, the opportunit y f or an operato r to def eat monitors in order to start -up
works must be considered a r isk and mitigated appropr iately . Simple r isk
mitigation methodology will also remove the impossible posit ion some
operators ar e put in where no f acilit y exists to deal with a qualit y pro blem
due to an inappropriate design of the works. Such mitigation may be as
simple as a run to waste f acilit y at treat ment works, where qualit y issues
are of ten seen dur ing initiation of a works or setting water qualit y trigge rs
appropr iately f or each site .
Secondar y events caused by initial event investigations
Lartington works near to Darlington is a large surf ace water tr eatment
typically supplying 110 Ml/d of treated water to a populat ion of
approximately 580,000 in the Teesdale and Teesside area. The site,
originally f rom the 1960s, treats raw wat er collected in f ive impounding
reser voirs and consists of two dif f erent clar if ication streams, pH correct ion
f or manganese removal bef ore rapid gravit y f iltr ation and f inally
disinf ection.
In August 2015, a single E.coli was detected and as part of the
investigation a remot e operated vehicle survey of the contact tanks was
undertaken. This technique allows companies to inspect tanks and
reser voirs f or signs of internal damage whil e st ill in supply. In Septembe r,
in preparat ion f or this survey, f low rates on the site wer e reduced to allow
the inspect ion to be undertaken. W hil e this in itself is not unusual, due
regard f or the operabilit y limits of a works must always be considered and
54
Western region
this should consider not on ly the upper limits , but the lower limits to
determine the hazar ds and likely consequence of an action which may
present a r isk. In this works the lower limit is , in part, gover ned by the
minimum dosing of lime which can be achieved by the pumps. W hen the
f lows were reduced, the works was operating at the minimum possible lim it
f or the lime dosing pumps. W hen the lime batch changed to a higher
concentration the pump could not dose any less to compensate f or this
change causing the pH to rise outside the cri tical limit. The eff ectiveness
of chlorine used f or disinf ection is partly based around the pH of the water
it is dosed into. The consequential ef f ect of this was f or disinfection to
drop to less than 30% of the W orld Health Organis ation recommended
minimum of 15mg.min/l. The company, as a reactive me asure, have set the
alarm to 22mg.min/l to ensure ther e is an earlier warning of problems,
however, the objective of risk analysis is to ident if y proactively conditions
which may occur based upon historic analy sis.
This site was subject to an earlier event in June where the company
sought to allow the plant to perf orm more eff ectively at low f lows, the
sudden change in f low r esulted in a problem with the clar if iers. W hil e this
was not exact ly the same situation , this was an example of the works
being asked to perf orm outside its operabilit y limits and should have
ser ved to identif y the risk of changes. The question arises theref ore as to
why the company had not carried out an appropr iate r isk assessment of a
site known to have had recent operabilit y problems prior to initiating an
investigation which reduced the out put to the minimum possible lim it
eliciting an event more serious than the one it was invest igating. Senior
managers should ensure that risk analysis is transf erred to risk
assessment and this inf ormation is taken into account and used to dir ect
f uture work which may be carr ied out by staff or contractors who do not
have an over view of the consequential ef fects on treatment pr ocesses.
Turbidit y event d ue to lime dosing failure – single point of failure
In October, it was reported that water with elevated turbidit y had been
leaving Legacy works, which supplies approximat ely 44,000 consumers in
Legacy and Rhos zones. This surf ace water works uses lime dos ing f or pH
correction to opt imise the coagulation pr ocess af ter which it passes
through rapid gravit y f ilters and then onto chlor ination where lime is added
once again to ensure a suitable pH f or disinf ection. The ef f ectiveness of
chlorine used f or disinf e ction is partly based around the pH of the water it
is dosed into and at Legacy work is measured by a single probe which also
controls the lime dosing adjustment.
In the week leading up to the event, the company exper ienced problems
with the pre-contact pH probe, in the f orm of drif t, when com pared to
55
Drinking water 2015
manual pH readings. The probe was cleaned, recalibrated and returned to
ser vice. However, the probe began to drif t again. The drif t caused f alse
pre-contact pH readings and the lime dosing system incr eased dos ing as it
tried to compensate. As the same probe controlled the dosing and
monitor ing, no alarms were triggered and the site did not auto shutdown.
W hile the result ing increase in pH was recorded by the f inal water pH
monitor, at the time t his was not link ed to alarms or the automatic
shutdown syst em. The event eventually manif ested as high f inal water
turbidit y f rom the excess lime. At that time, the site auto shutdown alarms
were set to respond to f iltered turbidit y, pre -contact chlorine and pre contact p H. As none of these alarms wer e triggered, water wit h turbidit y
>1NTU was presented f or disinf ection and entered supply f or a period of
approximately 15 hours wit h the pH r ising to 9.3.
The company installed a second pre - contact pH probe, so that monitor in g
and lime dosing cont rol are handled separately. This will prevent a repeat
of this event, as a single probe def ect cannot cause complete f ailure of the
pH control and monit oring. Additionally, monitors not previously linked to
alarms, including the f inal water pH probe are now alarmed, allowing
greater control of the works.
This event illustrates both the f ailur e to prevent inadequately treated and
disinf ected water ent ering supply f rom works and the f ailure to adequately
identif y the r isk of not having s eparate systems which control inter linked
critical processes consequent ly leaving the works without a r obust crit ical
measure, and subsequently and unknowingly losing control of the works. It
is questionable how such a basic element of risk control was mis sed and
why companies must ensure a site set up is f ully known and is appropr iate
f or its operation at all times. The not so obvious risk in all of this is the
eff ect of a raised pH, some two points over normal. How aggressive the
now highly alkaline water has become m ay not be truly known, but the risk
of metals from the net work should be considered as company director s are
reminded that they are responsible f or supplying water which must not be
aggressive.
No of f ences are currently under consider ation by the Inspectorate in
connection with any of the events that occurred in the region in 2015.
During 2015, Bournemouth W ater was pr osecuted f or supplying water unf it
f or human consumption and one count of f ailure to adequately operate a
treatment process. The case relat ed to an outbreak of cryptosporidiosis in
Bournemouth linked to the water supply.
The charges were br ought under Section 70 of the W ater Industry Act 1991
and Regulat ion 26 of the W ater Supply ( W ater Qualit y) Regulation 2000.
56
Western region
The company was f ined £20,000 on each of f our counts of water unf it plus
£5,000 f or the count of f ailure to adequately operate a treatm ent process,
totalling £85,000 and paid £48,772 towar ds prosecution costs and a £120
vict im surcharge.
57
Drinking water 2015
Chapter 6: Technical audit activity
Chapt er 6:

Descr ibes the audit strategy of the Inspectorate.

Summarises the outcome of audit activit y in 2015.

Highlights learning points f or the industr y.

Summarises the strategic AMP6 dr inking water impr ovement
programme.
The Inspectorate has o perated a risk -based approach to technical audit
since 2005 and no technical audit takes place without a reason .
Technical audit is the means by which the Inspector ate ver if ies whet her
companies ar e oper ating and maintaining water supplies in a sustainabl e
manner that is likely to secure a saf e , clean supply of drinking water int o
the f uture. Audit act ivities tak e a number of diff erent f orms:

Assessment of inf ormation provided by water companies.

On-site inspection of company records, procedures and plans.

Meet ings to challeng e the veracit y of specif ic plans, procedur es or
programmes of work.
For the purposes of the report the audit activities in 2015 are divided into
two tables. Table 22 summarises the outcomes of inspect ions , including
consumer complaint investigations. Table 23 covers the outcomes of audits
relat ing to the enf orcing of water qualit y improvements.
Table 22: Outcomes from inspections and consumer compl aint
investigations in 2015
Comp an y
Loc at i on an d
M ain fin din gs f rom a udit
re a son
Au di t f o cu s: Ab st r act ion an d t r eat m ent
Br is t o l W ater
P ur t o n wor k s –
Uns at is f ac t or y
Br om ate
 Fi lt er b e ds i na d eq u at e l y m a in ta i n ed
res u l t in g i n wee d i n t h e l au n de rs an d
th e s h ap e of th e u n der m edi a n o z zl e s
be i n g v is ib l e o n t he s u rf ac e.
 Cri t ic a l m eas ures of o per a ti o n we re n o t
c arr ie d o ut inc l u d in g m eas ur em ent of
th e m ed i a h e ig h t an d obs er v at i o n of
was h es .
 Pr oc e d ur es wer e i n ad eq u at e.
58
Western region
Comp an y
Ch o ld er to n
an d D is tr ic t
W ater
Loc at i on an d
re a son
Ch o ld er to n wor k s
M ain fin din gs f rom a udit
Uns at is f ac t or y
 Us e of a n a nt is c al a nt on s it e t ha t is n ot
an ap pr o ve d pr o duc t f or us e i n dr ink i n g
wa ter .
 No a l arm s o n s it e t o a l ert wh en
d is i nf ec t io n f ai ls ( bre a c h of R e gu l at i o n
26) an d c h l or in at i o n is o n l y m eas ur ed
m anua l l y o nc e p er d a y.
 Com pa n y d i d n ot h a v e i n p l ac e a
proc e d ure t o e ns u re t h e l en g th of t im e
s od i um h yp oc h lo ri t e w as s tor e d i n or de r
to m in im is e d is i nf ec t i o n b y - pro d uc ts a n d
c h lor at e f orm at io n R ec om m end e d
i ns t a ll a ti o n of t ur b id i t y m oni t or pr e
d is i nf ec t io n.
S ou th W es t
Cr o wn h i l l wo r k s –
Uns at is f ac t or y
W ater
l im e d os i ng
 S er v ic i n g a nd c a l i br at i on r ec or ds n ot up
f ai l ur es
to d a te .
 B ir ds an d f aec es s e e n o n l e dg e
o ver h a ng i ng c la rif ier s tre am .
 In ef f ic ie nt r ap i d gr a v it y f i lt er wa s h i n g.
 M is s e d c l ar if i er c l e an i ng da tes .
 S od i um h yp oc h lor i te d os in g p o in t
s ubm er ge d i n d ir t y wa t er, r is k of
i ngr es s /c o nt am in at i o n.
 S om e ac t io ns t ha t th e c om pan y h a d
c om m itt ed t o re g ard i n g l im e d os i ng wer e
no t c om pl et e d.
W es s ex
Dur l e ig h wor k s –
G e ner a l l y s at is f ac t or y
W ater
m ic r ob i ol o g ic a l a n d  Com pa n y i n pr oc es s o f m aj or s i t e
tur b id i t y f a i l ur es
up gr a de in v o l v in g t ot a l r e bu i l d of t h e
s it e o v er t he n ex t A M P p er io d d u e to
tak e t wo ye ars .
 Com pa n y d i d n ot h a v e i n p l ac e a
proc e d ure t o e ns u re t h e l en g th of t im e
s od i um h yp oc h lo ri t e w as s tor e d i n or de r
to m in im is e d is i nf ec t i o n b y - pro d uc ts a n d
c h lor at e .
 Ris k as s es s m en t f or s i te n o t up d at e d to
ref l ec t c u rre nt r is k s .
Au di t fo c u s: S e rv i ce re s e rv oi rs i nte gr it y a nd m an ag em ent
Ch o ld er to n
Ch o ld er to n t ank –
Uns at is f ac t or y
an d D is tr ic t
br e ak t ank au d its
 No re g u lar s am pl in g a t t h is as s e t a nd it
W ater
f its th e c r it er ia f or d ef i n it i on of s er v ic e
res e r vo ir .
 Com pa n y t o u pd at e as s et d ef i n i t i o n to
i nc l u de as s er v ic e r es er vo ir .
 Dis c us s ed ou tc om e of bre ak t ank au d its
b y br ief t o W ater U K.
59
Drinking water 2015
Comp an y
W es s ex
W ater
Loc at i on an d
re a son
M in et y T a nk 1 +2
W hyc h ur c h ta nk –
br e ak t ank au d its
M ain fin din gs f rom a udit
Uns at is f ac t or y
 No re g u lar s am pl in g a t t hes e as s ets an d
th e y f it t h e c r it er i a f or def in i t io n of
s er v ic e r es er v o ir.
 Com pa n y t o u pd at e as s et d ef i n it i o n to
i nc l u de as s er v ic e r es er vo irs .
 Dis c us s ed ou tc om e of bre ak t ank au d its
b y br ief t o W ater U K.
Au di t fo cu s: O t h e r
Br is t o l W ater
Pr ogr es s wit h
Pr o v is i o na l
E nf or c em ent O r der
f or f a i lur e t o n ot if y
a c r i tic a l e v e nt
ad e qu a te l y
Uns at is f ac t or y
 T he c o nc lus i o n of th e a u di t i d e nt if i e d
req u ir em ents wer e n o t be i ng m et d u e to
th e f ol l o wi n g k e y r e as ons :
 Fa i lur e t o d el i v er i n ter im tra i n in g t o
th e N et work Mo d el l i n g t eam or t h e
Me d i a a nd C om m un ic a ti o ns te am a s
ha d b e en t o I nc i d en t Ma n ag ers .
 T he Ne t work M o de l l i n g te am we re
no t a war e t he y we r e t he s in g l e po i nt
of c o n tac t f or de te rm in i ng p o pu l at i o n
af f ec t ed d ur i ng an e v e nt ef f ec t i v e
im m ed ia te l y, r a th er t h an on
c om pl et i on of t he Em erge nc y
Ma n ag em en t Im pro v e m ent pr oj ec t i n
Ma y 2 0 1 5.
 T he W ater Q u a l it y t e a m proc e d ur e
was d a te d S e pt em ber 20 1 2 a nd h a d
no t b ee n s u bj ec t t o r e v i e w res u lt i n g
i n f a i l ure t o n ot if y a l l q ua l if yi n g
e ve n ts .
 A r ec om m end a ti o n wa s m ade t o t he
Ch i ef I ns pec to r of Dr i n k ing W ater th at a
Fi na l Enf orc em e n t O rd er wo u l d b e
req u ir ed in ord er t o s e c ure c om pl ia nc e.
S ubs e qu e nt t o t his au d it t he O r de r was
pu t i n p l ac e in Apr i l 2 0 15 . T h e
req u ir em ents of t he O r der wer e s u bj ec t
to f urt h er a ud i t.
Br is t o l W ater
Fi na l Enf or c em en t
S at is f ac tor y
O r d er r e - au d it
 Re v oc at i o n of O rd er is s ue d i n A u g us t
20 1 5.
Au di t fo cu s: Co ns um er com pl ain t h and li n g
Br is t o l W ater
Il l n es s ( 1)
1 S at is f ac to r y
S ou th W es t
W ater
Dis c o l our a ti o n ( 2)
Le a d ( 2)
O th er ( 1)
P ar t ic u la tes ( 1)
T as te a n d od o ur
( 1)
7 S at is f ac to r y
60
Western region
During 2015, the Inspectorat e f ocused on two special areas within its audit
programme. Focusing on special ar eas is addit ional to the risk -based
programme described above and is usually where sites or assets are
outside the requirement f or companies to submit data under r egulator y
monitor ing, but have the potent ial to aff ect water qualit y. These areas
were f or structures called br eak tanks and f or bulk transf er of water.
Break tanks exist in net works f or operational reasons of ten to allow a
change of pressure from one area to the nex t or as a saf eguard against
backf low and are usually relat ively small. These are not consider ed to be
regulator y assets unlike a ser vice reser voir which are consider ed to be a
stored reser ve of water to meet a var iable demand and can be a range of
sizes sometimes containing millions of lit res of water.
These tanks represent a similar r isk in companies’ distribution systems as
ser vice reser voirs and can provide an access route f or external
contamination to ent er the water supply if not maintained. Unlike se r vice
reser voirs, monit oring is not specif ied in the Regulations and is lef t f or the
company to determine along with the risk assessment. The Inspectorate
has been not if ied of at least t wo events that included a microbiological
f ailure associated with a br eak tank and considered it appropriate to
establish their number and signif icance for drinking water qualit y.
Companies, when asked as part of the audit, declared 55 br eak tanks from
which the Inspector ate then carried out 13 site audits. The audits looked at
a number of aspects to develop an understanding of the tanks in use and
this included; age, construction, capacit y and the time water was retained
as well as qualit y considerat ions such as sampling, maintenance,
inspect ions and if they were within the company’s risk assessment.
Even though the Reg ulat ions do not specif y the monitor ing requirements of
break tanks, we would expect companies to treat them similar to service
reser voirs as they present a similar risk to the water supply. The
Inspectorat e con cluded that this was not the case. In tanks, which ranged
f rom 6 to 130 years, some were in ver y poor condit ion. W hile most
companies undertook weekly visits to tanks f or maintenance checks, the
internal inspect ion f requency was bet ween 1 – 15 years and some were
never inspected . The question ar ises ther ef ore; what were the companies
doing to assure them selves there were no developing qualit y problems? In
39 (71%) cases, ther e was no sampling at all and in 13 (24%) cases the
companies had not even included the tank in their risk assessment. Senior
managers of water companies are rem inded that they are responsible f or
completing risk assessments f or the whole supply syst em and not to do so
will result in enf orcement action.
Turning to the tanks themselves: The capacit ies of the tanks audited
var ied bet ween 359l up to 19.35Ml , the largest being about eight times the
61
Drinking water 2015
size of an Olympic swimming pool and the longest retent ion time, of those
which were known, was f ound to be over three days. Several sites were
f ound to have been previously designated as ser vice reser voirs and wer e
reclassif ied as break tanks. Senior managers must ask themselves, why in
some cases these ar e not a stored reser ve of water to meet a var iable
demand and why some were reclassif ied as tan ks, eff ectively increasing
the risk. Two companies have proact ively stated they will reclassif y their
break tanks as service reser voirs and commence regulator y sampling and
reporting. This has been taken into account in the f or ward plan f or the
Inspectorat e and sit es which were identif ied as a risk, or incorrectly
classif ied, will be the subject of f urther audits.
The second special area of interest in 2015 was water companies’
arrangements f or bulk transf ers. The wat er industr y has many
interconnections wi t hin and bet ween wat er companies that allow the
interchange of water to ensure a suf f icient volume is available. These
supplies are ref erred to as bulk transf ers or bulk supplies. W hen a
company supplies water to another company both ar e responsible in thi s
arrangement. That means water must be wholesome when exported and
must not cause a det eriorat ion to the syst em at a later point by the eff ects
of the change in the source. Equally, the importer must ensure they have
taken measures to secure suitable wate r f or their system. This is achieved
through inf ormation sharing and a combined risk assessment ahead of any
transf er.
In North London during 2012 an export of water f rom one company to
another result ed in a taste and odour event, this was reported in Dr inking
water 2012. In response, companies undertook to share quality inf ormation
and up-to- date knowledge of the status of all bulk transf ers (including both
inter-company and intra -company transf ers). However, dur ing 2013, t wo
events were not if ied to the In spector ate where a bulk transf er connect ion
was in place, but the companies involved did not know if it was in
operat ion or which consumers were ser ved by it.
In 2015, the Inspect orate ident if ied f urther evidence that weaknesses
existed in the protocols a nd arrangement s f or bulk supplies. The
Inspectorat e instigated an audit to establish the current status of
arrangements f or bulk transf ers and their f itness f or purpose, the
strategies f or operating bulk transf ers, communicat ion wit h receiving
companies, a nd sharing of water qualit y data. In total, 24 companies were
audited and one was select ed f or a site audit to assist with a more detailed
inspect ion of communications bet ween supplying and recipient water
companies.
As a f orwar d strategy f or companies to develop their resource and
resilience plan involving bulk transf ers, it would be expected that senior
62
Western region
managers would, by 2015, have clear f ramework agreements and risk
assessments to ensure water qualit y is the highest pr ior it y. The
Inspectorat e was theref ore disappointed t o identif y 25% of the companies’
bulk transf er protocols did not include a r egular transf er of data or
interact ion bet ween provider and recipient company , nor had the majorit y
of arrangements audited been reviewed or updated since being i ntroduced
in 2012. Companies f ailed to share risk assessments, water qualit y dat a or
any other water qualit y risk mitigation approach f or supplies bet ween
companies or within companies. Companies should ensur e that they ar e
f ully aware of the risks when ex porting or importing water and they have
taken all st eps to assess the risk to both companies.
The Inspectorate as part of its better regulat ion strat egy, shared with the
industr y the f indings from these audits in November 2015 at W aterUK. As
best pract ice, the advice to companies has been incorpor ated into the
revised guidance of the Regulations, curr ently in consultat ion and
scheduled f or release in early summer 2016.
Table 23 summarises the Inspector ate’s activit y in relation to
improvements to wat er qua lit y. These activities cover the putting in place
of Notices or undert akings and the checks made to ensure the work
specif ied by the company is technically appropr iate, has been carried out
in the required timescales and the benef its to water qualit y have been
realised.
Table 23: Outcome of audit acti vities relating to enforcing w ater
qualit y improvements
Ac t iv it y
Is s u i ng of
s ta tu t or y
i ns tr um ents
Re v i e wi ng
s c hem es
Ch a ng es of
s o lu t io n
Cl os ur e of
s c hem es
Ins p ec t i on of
s c hem es
Rec e ip t of r is k
as s es s m e nts *
Numb e r of imp rov em ent p rog ra mm e s ( and out com e s)
E nf or c em ent or d er is s ue d t o B RL ( 1)
No t ic es :
S BW ( 1) , SW T (1 )
Sc hem es r e v i e wed :
BR L ( 1 2) , CHO ( 1), SB W (2), SW T (17), W SX (2 8 ) ,
Sc hem es ex am in ed :
S BW ( 1) SW T (1) W SX (1)
Sc hem es r e v i e wed f or c l os ur e :
S at is f ac tor y – s c hem e c l os ed .
BR L ( 2) , SW T (3 ) W SX (3)
No n e du r i n g p er io d.
BR L ( 2 1 ,2 5 9) , C HO ( 9 8) , S BW (248) , SW T (13 , 16 3) ,
W SX ( 18 , 6 05)
* Th e s e f i g u r e s r e p r e s e n t l i n e s o f d a t a r e p o r t e d t o t h e I n s p e c t o r a t e . Th e o u t c o m e o f t h e
2
r e vi e w o f t h e d a t a c a n b e f o u n d i n t h e I n s p e c t o r a t e ’ s n e w q u a r t e r l y r e p o r t .
2
h tt p: // d wi . def r a . go v .u k /ab ou t/ a nn u al - re p ort / 20 1 6/ i nd ex .h tm l
63
Drinking water 2015
From Table 23 it can be seen that a ll schemes reviewed were satisf actory.
For further inf ormation on the Water Supply (Water Quality) Regulations
2000, or the m icrobiological and chemical parameters covered by the
regulations please r efer to the DWI website ( www.dwi.defra.gov.uk ).
If you have a need f or more specific information than that on our website,
please contact us on the DWI enquiry line: 0300 068 6400 .
64
Western region
Annex 1
Further sources of information
The reports and other content are published on the DW I website only
(www. dwi.def ra.gov. uk).
The publication Dr inking water 2015 comprises the regional r eports f or
England and a report covering W ales. There are f our regional reports f or
England (Central and Easte rn, London and South East, Northern, and
W estern) and one f or W ales (in t wo lang uages). Each report presents
inf ormation f rom 2015 under the f ollowing headings:






Summar y.
W ater supply arrang ements.
Drinking water qualit y test ing.
Drinking water qualit y results.
Drinking water qualit y events.
Technical audit activit y.
There are also separ ate reports covering private water supplies, one
cover ing England and one covering W ales (in t wo languages).
Water company look -up tables
These summarise all the resu lts of water company monitor ing in 2015.
They provide inf ormation on:




what was tested;
how many tests were perf ormed;
the range of the results of testing; and
how many tests f ailed to meet the standards.
Significant drinking w ater quality events in Engla nd and
Wales 2015
To promote shared learning, the Inspect orate has compiled a list of all
signif icant, serious and major events that occurred in 201 5, which
illustrates the nature and cause of each event, the main actions by the
company and f indings f rom the inspector s’ assessments. Relevant content
f rom this overall list is cont ained in an annex to each regional report.
65
Drinking water 2015
Annex 2
Information relating to public water supplies published by the
Inspectorate in 2015
Information Letters
Ref
Title
01/201 5
Regulation 28 reporting requirements
02/2015
Legal Instruments – Processes f or reporting on, agreeing
changes to and closure/revocat ion
03/2015
Regulation 31 approval of products and substances intended f or
disinf estation, disinfection or cleaning agents o f water works
apparat us and distribution systems
04/201 5
Publicat ion of a research report on the signif icance of chromium
in dr inking wate r
05/2015
Publicat ion of resear ch: Understanding the impl ications of the
European requirements relat ing to radon in dr inking water
The letters, and their associated annexes, can be found on the Inspectorate’s website at
h t t p : / / w w w. d wi . d e f r a . g o v . u k / s t a k e h o l d e r s / i n f o r m a t i o n - l e t t e r s / i n d e x. h t m
Technical guidance

W orld Health Organisation technical br ief – Boil water
C o p i e s o f t h e a b o v e g u i d a n c e c a n b e f o u n d o n t h e I n s p e c t o r a t e ’ s we b s i t e a t
h t t p : / / w w w. d wi . d e f r a . g o v . u k / s t a k e h o l d e r s / g u i d a n c e - a n d - c o d e s - o f - p r a c t i c e /
66
Western region
Research
Ref
Title
DW I 70/2/223
Free-Living protozoa and opportunist ic pathogens in
distr ibuted water
DW I 70/2/256
Risk assessment of VTEC inf ections in English and W elsh
drinking water
DW I 70/2/261
Eff ective microbial control strategies f or main breaks and
depressurization
DW I 70/2/275
Under standing the signif icance of chromium in dr inking
water
DW I 70/2/281
National assessment of the risks to water supplies posed
by low taste and odour threshold compounds
DW I 70/2/292
Volatile organic com pounds – Understanding the risks to
drinking water
DW I 70/2/300
Eff ect of UV on the chemical composition of water
including disinf ection byproduct f ormation
DW I 70/2/301
Under standing the implication of the EC’s proposals
relat ing to radon in drinking water f or the UK
C o p i e s o f r e s e a r c h r e p o r t s a n d e x e c u t i v e s u m m a r i e s c a n b e f o u n d o n t h e I n s p e c t o r a t e ’ s we b s i t e
at http:// www.dwi.defra.gov.uk/research/completed
67
Drinking water 2015
Annex 3
Not significant and minor drinking water quality events
Nature
Number of not significant and minor events
WSX (1)
Area affected (estimate of population affected)
U p t o n S c u d a m o r e , W i l t sh i r e ( 1 1 , 1 6 6 )
BRL (1)
W ri t h l i n g t o n , S o m e r s e t ( 3 )
Chemical
WSX (2)
Discolouration
BRL (1)
Poole, Dorset (3)
Ye o vi l , S o m e r s e t ( 3 )
H e n b u r y, B r i s t o l ( 1 1 , 7 5 0 )
A i r i n w a t e r ( wh i t e )
BRL (3)
Loss of supplies/
poor pressure
Bristol (10,000)
Long Ashton, Bristol (5,688)
W el l s , S o m e r s e t ( 8 , 2 5 0 )
P l ym o u t h , D e vo n ( 7 , 0 0 0 )
SW T ( 1 )
WSX (2)
S wa n a g e , D o r s e t ( 4 , 0 0 0 )
To l l e r P o r c o r u m , D o r s e t ( 3 2 5 )
B a c k we l l , N o r t h S o m e r s e t ( 3 )
BRL (1)
SW T ( 3 )
W ad e b r i d g e , C o r n w a l l ( 7 , 0 0 0 )
P l ym o u t h , D e vo n ( 3 )
S t J u s t , C o r n wa l l ( 3 , 5 0 0 )
B r i d g wa t e r , S o m e r s e t ( 3 )
Mi c r o b i o l o g i c a l
WSX (1)
Other
SW T ( 2 )
E xe t e r , D e vo n ( 1 )
E a s t B u d l e i g h a n d s u r r o u n d i n g a r e a s , D e vo n ( 5 , 0 0 0 )
Bedminster, Bristol (3,370)
G l a s t o n b u r y, S o m e r s e t ( 3 )
K i n g s b r i d g e , D e vo n ( 6 , 2 5 0 )
O k e h a m p t o n , D e vo n ( 3 )
S i d m o u t h , D e vo n ( 3 )
S a l c o m b e R e g i s , D e vo n ( 3 )
To r p o i n t , C o r n w a l l ( 3 )
Broadstone, Dorset (3)
C r e wk e r n e , S o m e r s e t ( 3 )
Poole, Dorset (3)
Salisbury, W iltshire (5)
Stubhampton (5)
BRL (2)
SW T ( 5 )
Public concern
WSX (5)
68
Western region
Nature
Number of not significant and minor events
BRL (3)
WSX (1)
Area affected (estimate of population affected)
Bristol (3)
Mi l t o n , S o m e r s e t ( 1 )
Pilning, Gloucestershire (3)
Mi l l b r o o k , C o r n w a l l ( 3 )
P e n za n c e , C o r n wa l l ( 3 )
Port Isaac, Cornwall (3)
S o u t h Mi l t o n , D e vo n ( 3 )
W ar m i n s t e r , W i l t s h i r e ( 3 )
38 – BRL (11), SWT (15), WSX (12)
83,374
SW T ( 4 )
Ta s t e o r o d o u r
Total
Significant, serious and major drinking water quality events
Date and
duration
Area
12 Jan 2015
F o r 3 d a ys
(W S X)
C u r r y R i ve l ,
Somerset
Estimate of
population
affected
500
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Loss of
supplies/poor
pressure due to
burst main.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Sampled affected area.

Repaired main.

R e zo n e d a r e a ( b r o u g h t i n wa t e r f r o m d i f f e r e n t s o u r c e ) .
DWI comments and findings:

Ma i n r e p a i r e d a n d n e t wo r k r e t u r n e d t o o r i g i n a l
configuration.
Risk classification: Significant
69
Drinking water 2015
Date and
duration
Area
21 Jan 2015
F o r 3 0 d a ys
(W S X)
Chippenham,
W il t s h i r e
Estimate of
population
affected
3
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Do not drink notice
d u e t o wa t e r f i t t i n g s
c o n t r a ve n t i o n s .
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Issued a do not drink notice to a school in
Chippenham.

Carried out a fittings inspect ion.

B e l a t e d l y i s s u e d a N o t i c e r e q u i r i n g t h e c o n t r a ve n t i o n s
identified to be rectified.
DWI comments and findings:

Inadequate training/competence of staff.

S a m p l i n g wa s n o t t i m e l y e n o u g h .

Inadequate communication caused delay in response.

Inadequate procedures.

R e c o m m e n d a t i o n t o i m p r o ve p r o c e d u r e s f o r e s c a l a t i o n
a n d u n d e r s t a n d i n g o f s a m p l e e xc e e d a n c e s .

Ensure procedures and training of staff sufficiently
robust to understand company obligations when
failures occur in public buildings .

C o m p a n y t o s e r ve S e c t i o n 7 5 N o t i c e s .
Risk classification: Significant
30 Jan 2015
For 12 hours
(W S X)
Alton Pancras
works, Dorset
7,592
Tu r b i d i t y o f 1 . 0 N T U
i n t h e t r e a t e d wa t e r
due to pipe
corrosion.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Replaced a deteriorating section of pipe within the
treatment works.
DWI comments and findings:

No further action to be taken.
Risk classification: Significant
70
Western region
Date and
duration
Area
17 Feb 2015
F o r 3 we e k s
( SW T)
Chumleigh,
D e vo n
Estimate of
population
affected
5
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Contamination of
p r i va t e t a n k
s u p p l yi n g t w o
properties.
South West Water Ltd action:

I s s u e d a b o i l wa t e r n o t i c e .

Sampled affected area.

B a c k f l o w p r o t e c t i o n i n s t a l l e d t o p r e ve n t c o n t a m i n a t i o n
o f t h e p u b l i c s u p p l y.

Ta n k w a s d i s c o n n e c t e d a n d n e w s u p p l y m a i n i n s t a l l e d .
DWI comments and findings:

No further action to be taken.
Risk classification: Significant
18 Feb 2015
F o r 2 d a ys
( SW T)
P l ym o u t h
3,750
Burst main causing
flooding of local
shops and
subsequent
discolouration.
South West Water Ltd action:

Sampled affected area.

Repaired main.

A l l s a m p l e s we r e s a t i s f a c t o r y.
DWI comments and findings:

No further action to be taken.
Risk classification: Significant
24 Feb 2015
F o r 4 d a ys
( SW T)
Ti ve r t o n , D e vo n
3
B r o wn
discolouration
a f f e c t i n g Ti ve r t o n
Hospital, due to
burst main by third
party.
South West Water Ltd action:

P r o vi d e d a n a l t e r n a t i ve s u p p l y b y t a n k e r / b o ws e r .

P r o vi d e d b o t t l e d wa t e r o n r e q u e s t .

Sampled affected area.

Flushed mains.
DWI comments and findings:

S a m p l e s n o t a n a l ys e d f o r a p p r o p r i a t e p a r a m e t e r s .

R e c o m m e n d a t i o n t o r e vi e w a n d r e vi s e s a m p l i n g
p r o c e d u r e s f o r s e n s i t i ve c u s t o m e r s .
Risk classification: Significant
71
Drinking water 2015
Date and
duration
Area
1 3 Ma r 2 0 1 5
F o r 4 we e k s
(W S X)
Cattistock
works,
Dorchester
Estimate of
population
affected
1,387
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Mi c r o b i o l o g i c a l
contamination.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

S h u t d o wn t r e a t m e n t wo r k s b u t wi t h s o m e d e l a y .
DWI comments and findings:

I n a d e q u a t e i n ve s t i g a t i o n s i n t o r o o t c a u s e .

Recommendation made that company should respond
more promptly to the detection of microbial indicators
a s s o c i a t e d wi t h t h e d e t e r i o r a t i o n o f r a w wa t e r q u a l i t y .
Risk classification: Significant
2 6 Ma r 2 0 1 5
For 1 day
(BRL)
B a r r o w wo r k s ,
South Bristol,
North Somerset
and South
Gloucester
346,915
Bristol Water Plc action:

R e p l a c e d s a m p l i n g f a c i l i t y.

R e vi e w o f p r o c e d u r e s .

Sampled affected area.
Mi c r o b i o l o g i c a l
contamination.
DWI comments and findings:

Th e c o m p a n y ' s f i n a l r e p o r t wa s n o t s u f f i c i e n t l y d e t a i l e d
r e q u i r i n g f u r t h e r q u e s t i o n s t o b e a n s we r e d t o c o m p l e t e
t h e e ve n t ' s a s s e s s m e n t .
Risk classification: Significant
3 1 Ma r 2 0 1 5
F o r 1 5 d a ys
(BRL)
South Bristol,
North Somerset
and South
Gloucester
244,325
Bristol Water Plc action:

Flushed mains.

Sampled affected area.

Initiated powdered activated carbon dosing at the
s u p p l yi n g t r e a t m e n t w o r k s ( B a r r o w ) .
Ta s t e a n d o d o u r
d u e t o r a w wa t e r
deterioration at
B a r r o w wo r k s .
DWI comments and findings:

Inadequate contingency planning.

Company acted promptly to customer contacts , but
recommended that adequate measures are in place to
p r e ve n t wa t e r wh i c h i s a e s t h e t i c a l l y u n a p p e a l i n g b e i n g
supplied to customers.
Risk classification: Significant
72
Western region
Date and
duration
Area
02 Apr 2015
F o r 6 we e k s
( SW T)
P l ym o u t h ,
D e vo n
Estimate of
population
affected
8
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Ground
contamination due
to spillage,
affecting industrial
site.
South West Water Ltd action:

Sampled affected area.

Issued a do not drink notice to the affected premises.

R e p l a c e d s e r vi c e wi t h b a r r i e r p i p e .

P r o vi d e d a n a l t e r n a t i ve s u p p l y b y t a n k e r / b o ws e r .
DWI comments and findings:

R e m e d i a l wo r k s we r e c o m p l e t e d , t h e d o n o t d r i n k
n o t i c e wa s l i f t e d a n d s a t i s f a c t o r y s a m p l e s o b t a i n e d .
Risk classification: Significant
05 Apr 2015
F o r 2 d a ys
(W S X)
Ye o vi l
25
Loss of supplies
and risk of
microbiological
contamination due
to burst main.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Flushed mains.

I s s u e d a b o i l wa t e r n o t i c e .

P r o vi d e d a n a l t e r n a t i ve s u p p l y b y t a n k e r / b o ws e r .

P r o vi d e d b o t t l e d wa t e r o n r e q u e s t .

Repaired main.

R e zo n e d a r e a ( b r o u g h t i n wa t e r f r o m d i f f e r e n t s o u r c e ) .

Sampled affected area.
DWI comments and findings:

C r i t i c a l o f c o m m u n i c a t i o n s b e t we e n t h e r e p a i r t e a m
a n d t h e s u p e r vi s o r , h o w e ve r t h e c o m p a n y h a s b r i e f e d
staff on the importance of health and safety for future
scenarios.
Risk classification: Significant
73
Drinking water 2015
Date and
duration
Area
07 Apr 2015
F o r 6 we e k s
(W S X)
Poole, Dorset
Estimate of
population
affected
3
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Ground
contamination due
to spillage.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Issued a do not drink notice to industrial premises in
Poole.

Sampled affected area.

Flushed mains.

R e p l a c e d m a i n wi t h b a r r i e r m a t e r i a l .

S a m p l e s t a k e n a n d r e s u l t s s a t i s f a c t o r y.
DWI comments and findings:

No further action to be taken.
Risk classification: Significant
15 Apr 2015
F o r 1 we e k
(W S X)
Ford, Salisbury,
W il t s h i r e
5
Risk of
contamination from
a p r i va t e s u p p l y
due to illegal cross
connection.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Company carried out a fittings inspection.

N o t i c e s e r ve d o n p r i va t e s u p p l y o w n e r f o r r e m e d i a l
work.

F i t t e d a b a c k f l o w v a l ve t o p r o t e c t t h e s u p p l y .

Sampled affected area.

Th e c o m p a n y r e s p o n d e d d i l i g e n t l y t o t h e i s s u e s
presented.
DWI comments and findings:

B o i l wa t e r a d vi c e i s s u e d t o p r o p e r t i e s b y l o c a l
a u t h o r i t y.

W il t s h i r e C o u n c i l i s wo r k i n g wi t h t h e o wn e r o f t h e
p r i va t e s u p p l y t o r e s o l ve i s s u e s .

Th e o w n e r h a s b e e n g i v e n t wo m o n t h s t o c o m p l e t e t h e
necessary works to comply with regulations, if works
h a ve n o t c o m m e n c e d wi t h i n t h i s t i m e t h e y wi l l s e e k t o
s e r ve a R e g u l a t i o n 1 8 N o t i c e .
Risk classification: Significant
74
Western region
Date and
duration
Area
21 Apr 2015
F o r 6 d a ys
(W S X)
W as h p o o l
works, Bath
Estimate of
population
affected
102,260
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Accidental
o ve r d o s i n g o f
phosphoric acid due
to back siphonage.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Repaired faulty equipment.

R e vi e w o f p r o c e d u r e s .

R e p l a c e d s o l e n o i d va l ve .

I n s t a l l e d l o a d i n g va l ve t o p r e v e n t d o s i n g o f c h e m i c a l
w h e n n o w a t e r f l o w.

R e vi e w e d r e p o r t i n g p r o c e d u r e s f r o m t h e l a b o r a t o r y t o
ensure a timely response.

C a r r i e d o u t a w i d e r r e vi e w o f c h e m i c a l d o s i n g a n d
m a d e a n y n e c e s s a r y i m p r o ve m e n t s .
DWI comments and findings:

Inadequate risk assessment.

Inadequate procedures.

Inadequate contingency planning.

N o m i t i g a t i o n f o r f a i l u r e o f va l ve s .

Update risk assessment.

Recommend that chemical dosing tanks are isolated
before planned work is carried out on treatment works.

R e c o m m e n d t h a t t h e c o m p a n y r e vi e w i t s P r o c e s s R i s k
A s s e s s m e n t a n d e n s u r e s wa t e r q u a l i t y r i s k s a r e
adequately considered and mitigated .
Risk classification: Significant
22 Apr 2015
For 48 hours
(BRL)
E a s t vi l l e ,
Bristol
1,548
Loss of supply and
media interest
f o l l o wi n g a b u r s t
main.
Bristol Water Plc action:

Repaired main.

P r o vi d e d b o t t l e d wa t e r o n r e q u e s t .

Sampled affected area.

Flushed mains.

S a m p l e s we r e s a t i s f a c t o r y.
DWI comments and findings:

Ma i n w a s r e p a i r e d a n d b u r s t a g a i n o n r e c h a r g e .
Risk classification: Significant
75
Drinking water 2015
Date and
duration
Area
28 Apr 2015
F o r 3 we e k s
(W S X)
W e ym o u t h ,
Dorset
Estimate of
population
affected
5
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Consumer concern
due to cross
connections and
back siphonage.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

F i t t i n g s i n s p e c t i o n c a r r i e d o u t wh i c h i d e n t i f i e d
backflow from a cistern.

C h e c k va l ve s i n s t a l l e d .
DWI comments and findings:

Th r e e p r o p e r t i e s h a d c o n n e c t e d wa t e r s u p p l i e s , o n e o f
t h e s e wa s a c o m m e r c i a l f o o d o u t l e t .
Risk classification: Significant
0 1 Ma y 2 0 1 5
For 1 day
(BRL)
L i t t l e t o n wo r k s ,
South
Gloucestershire
258,503
Bristol Water Plc action:

Sampled affected area.

R e vi e w o f p r o c e d u r e s .

A root cause was not identified.

D a t a p r o vi d e d s u g g e s t t h a t t h e r e w a s n o l o s s i n
disinfection.
Mi c r o b i o l o g i c a l
contamination.
DWI comments and findings:

Required company to confirm disinfection
arrangements.
Risk classification: Significant
02 Jun 2015
F o r 6 we e k s
(W S X)
L yt c h e t t
Ma t r a ve r s
3
Ta s t e o r o d o u r d u e
to ground
contamination.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

I s s u e d a d o n o t d r i n k n o t i c e t o a s c h o o l i n L yc h e t t
Ma t r a ve r s .

Sampled affected area.

P r o vi d e d b o t t l e d wa t e r o n r e q u e s t .

P r o vi d e d a n a l t e r n a t i ve s u p p l y b y t a n k e r / b o ws e r .

P r i va t e p i p e w o r k w a s r e n e we d .
DWI comments and findings:

Th e d o n o t d r i n k n o t i c e w a s l i f t e d f o l l o w i n g i n s t a l l a t i o n
of new pipework to the centre and satisfactory sample
results.
Risk classification: Significant
76
Western region
Date and
duration
Area
11 Jun 2015
F o r 6 we e k s
( SW T)
Sidmouth
Estimate of
population
affected
10
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
B o i l wa t e r n o t i c e t o
three properties
due to leaking
s e r vi c e j o i n t
situated inside a
s e we r c h a m b e r .
South West Water Ltd action:

Sampled affected area.

I s s u e d a b o i l wa t e r n o t i c e .

Fittings inspection carri ed out.

E l e va t e d l e a d d e t e c t e d , r e s i d e n t s a d vi s e d t o r e p l a c e
l e a d p i p e wo r k .
DWI comments and findings:

R e m e d i a l wo r k c o m p l e t e d s a t i s f a c t o r i l y a n d t h e b o i l
w a t e r n o t i c e wa s l i f t e d .
Risk classification: Significant
17 Jun 2015
For 20 weeks
(W S X)
Poole, Dorset
43
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Issued a do not drink notice to an industrial estate in
Poole.

P r o t e c t e d t h e p u b l i c s u p p l y.

Sampled affected area.

Company issued a Notice to the landowner to replace
t h e c u r r e n t p i p e n e t w o r k wi t h b a r r i e r p i p e .
Ta s t e a n d o d o u r
due to ground
contamination.
DWI comments and findings:

A l l t h e s e r vi c e s a s s o c i a t e d wi t h t h e i n d u s t r i a l u n i t s
h a ve n o w b e e n r e p l a c e d wi t h p r o t e c t i ve l i n e d p i p e .
Risk classification: Significant
18 Jun 2015
For 1 day
(BRL)
Nailsea
8
Bristol Water Plc action:

Sampled affected area.

P r o vi d e d b o t t l e d wa t e r o n r e q u e s t .

R e p l a c e d s e r vi c e p i p e s ( a n d r e m o ve d c o n t a m i n a t i n g
ingress point).

S a t i s f a c t o r y s a m p l e s we r e o b t a i n e d .
Mi c r o b i o l o g i c a l
contamination.
DWI comments and findings:

Company has confirmed that all mitigation work has
b e e n c o m p l e t e d a n d s u p p l i e s h a ve b e e n r e s t o r e d .
Risk classification: Significant
77
Drinking water 2015
Date and
duration
Area
19 Jun 2015
For 1 day
(W S X)
D o wn E d g e ,
Bath
Estimate of
population
affected
3
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Consumer concern
due to spring water
connection.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

I s s u e d a b o i l wa t e r n o t i c e .
C o n n e c t e d t h e t h r e e p r o p e r t i e s t o a p o t a b l e s u p p l y.

Disconnected spring water supply.
Conducted a company-wide scheme to remediate any
o t h e r p r o p e r t i e s wi t h s i m i l a r s u p p l y a r r a n g e m e n t s .
DWI comments and findings:

I n s p e c t o r a t e p r o vi d e d g u i d a n c e a n d a d vi c e f o r t h e
c o m p a n y t o r e s o l ve t h e h i s t o r i c s u p p l y i s s u e s a t t h e
properties.
Risk classification: Significant
26 Jun 2015
For 28 weeks
(W S X)
Tr o wb r i d g e ,
W il t s h i r e
3
Consumer concern,
f o l l o wi n g c o m p l a i n t
of illness due to
back-siphonage.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Sampled affected area.

Carried out fittings inspection.
DWI comments and findings:

C o n f i r m e d r e m e d i a l wo r k s a t i s f a c t o r i l y c o m p l e t e d .
Risk classification: Significant
29 Jun 2015
F o r 3 d a ys
(W S X)
Lopcombe,
W il t s h i r e
3
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Carried out fittings inspection.

I s s u e d a b o i l wa t e r n o t i c e t o t h e a f f e c t e d p r o p e r t y.

Sampled affected area.

I s s u e d a d vi c e o n t a p h y g i e n e .
Mi c r o b i o l o g i c a l
contamination.
DWI comments and findings:

Th e c o m p a n y i n ve s t i g a t i o n d i d n o t i d e n t i f y a n y w i d e r
issues.
Risk classification: Significant
78
Western region
Date and
duration
Area
13 Jul 2015
F o r 5 d a ys
(W S X)
F o r s t o n wo r k s ,
Dorset
Estimate of
population
affected
17,961
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Compromised
disinfection due to
chlorination
equipment failure.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

S h u t d o wn t r e a t m e n t wo r k s .

Repaired faulty equipment.

Sampled affected area.
DWI comments and findings:

Mi n d e d t o m a k e r e c o m m e n d a t i o n s r e g a r d i n g f a i l i n g s
w h i c h l e d t o t h e e ve n t . H o we ve r , i t w a s n o t e d t h a t t h e
c o m p a n y t o o k s t e p s t o p r e ve n t a r e c u r r e n c e .
Risk classification: Significant
17 Jul 2015
For 1 day
( SW T)
W in k l e i g h ,
D e vo n .
1,800
B r o wn
discolouration due
t o e m e r g e n c y wo r k .
South West Water Ltd action:

Flushed mains.

R e vi e w o f p r o c e d u r e s .
DWI comments and findings:

Lack of maintenance of equipment.

A n a v o i d a b l e e ve n t c a u s e d p r i m a r i l y b y l i m e d o s i n g
e q u i p m e n t f a i l u r e a t t h e s u p p l yi n g w o r k s ( P r e wl e y)
l e a d i n g t o wo r k s s h u t d o w n a n d c o n s e q u e n t r e z o n i n g t o
maintain supplies.

Recommended to ensure that turbidity monitors at the
s u p p l yi n g w o r k s a r e m a i n t a i n e d t o p r o vi d e r e l i a b l e
readings at all times.
Risk classification: Significant
79
Drinking water 2015
Date and
duration
Area
31 Jul 2015
F o r 3 d a ys
(W S X)
Boscombe,
Salisbury
Estimate of
population
affected
5
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Ta s t e a n d o d o u r
due to coal tarlined distribution
mains.
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Do not drink notice issued to affected properties.

R e vi e w o f p r o c e d u r e s f o r r e s p o n d i n g t o t a s t e a n d
o d o u r c o n t a c t s l i n k e d t o t h e p r e s e n c e o f h yd r o c a r b o n s .

W at e r m a i n r e p l a c e d .
DWI comments and findings:

S a m p l e s n o t a n a l ys e d f o r a p p r o p r i a t e p a r a m e t e r s .

Inadequate follow-up sampling.

Recommended to ensure sufficient and timely sampling
a n d a n a l ys i s i s c a r r i e d o u t .
Risk classification: Significant
03 Aug 2015
F o r 2 d a ys
( SW T)
D a wl i s h
13,500
B r o wn
discolouration due
to burst main.
South West Water Ltd action:

R e zo n e d a r e a .

Sampled affected area.

Repaired main.
DWI comments and findings:

Inadequate risk assessment.

I n a d e q u a t e i n ve s t i g a t i o n s i n t o r o o t c a u s e .

S a m p l i n g wa s n o t t i m e l y .
Risk classification: Significant
80
Western region
Date and
duration
Area
26 Aug 2015
F o r 3 we e k s
( SW T)
N o r t h D e vo n
Estimate of
population
affected
237,837
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Ta s t e a n d o d o u r
d u e t o r a w wa t e r
deterioration.
South West Water Ltd action:

Sampled affected area.

B l e n d e d s u p p l y wi t h a n o t h e r s o u r c e .

Installed additional treatment (to remain in place until
t h e wo r k s i s u p g r a d e d l a t e r i n t h e A MP p e r i o d ) .
DWI comments and findings:

Th e e ve n t wa s c a u s e d b y i n c o r r e c t l y c a l i b r a t e d
t e l e m e t r y wh i c h p e r m i t t e d a i r t o b e s u c k e d i n t o t h e
m a i n vi a t h e s u c t i o n t a n k .

Th e i s s u e o f f a u l t y s e t t i n g o f t e l e m e t r y l e ve l s f o r
s u c t i o n t a n k s h a s b e e n i n c o r p o r a t e d i n t o a r e vi s e d
p r o c e d u r e f o r p l a n n e d w o r k o n s u c h a s s e t s t o p r e ve n t
a recurrence.
08 Sep 2015
F o r 4 d a ys
(W S X)
Bratton
S e ym o u r ,
Somerset
775
Risk classification: Significant
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

P r o vi d e d b o t t l e d wa t e r o n r e q u e s t .

I s s u e d a b o i l wa t e r n o t i c e .

R e m o ve d s e r vi c e r e s e r v o i r f r o m s u p p l y.

I n s p e c t e d s e r vi c e r e s e r v o i r a n d r e p a i r e d a p o i n t o f
ingress.

C o m p a n y - wi d e r e vi e w t o i d e n t i f y d e f e c t s i n o t h e r
s e r vi c e r e s e r v o i r s .
Introduced a water quality impacts programme to
ensure assets are suitably maintained.
Mi c r o b i o l o g i c a l
contamination of
B r a t t o n S e ym o u r
N e w s e r vi c e
r e s e r vo i r .
DWI comments and findings:

Inadequate risk assessment.

Inadequate procedures.

Th e I n s p e c t o r a t e c o m p l e t e d a s i t e vi s i t t o s e e t h e wo r k
a l r e a d y c o m p l e t e d b y t h e c o m p a n y.

Th e f r e q u e n c y o f w a t e r q u a l i t y s i t e a s s e s s m e n t s t o b e
identified using a risk-based approach.

Risk assessments to be resubmitted to the
Inspectorate.
Risk classification: Serious
81
Drinking water 2015
Date and
duration
Area
03 Oct 2015
For 48 hours
( SW T)
S t B l a ze y,
C o r n wa l l
Estimate of
population
affected
50,000
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Me d i a i n t e r e s t d u e
to burst main.
South West Water Ltd action:

B yp a s s e d s e r vi c e r e s e r v o i r .

Flushed mains.

P r o vi d e d a n a l t e r n a t i ve s u p p l y b y t a n k e r / b o ws e r .

P r o vi d e d b o t t l e d wa t e r o n r e q u e s t .

Repaired main.

Sampled affected area.

R e vi e w e d t h e c o n d i t i o n o f t h e m a i n s a n d c o n s i d e r e d a n
ongoing flushing programme.
DWI comments and findings:

S u g g e s t e d t h a t t h e c o m p a n y r e vi e w s i t s c o n t i n g e n c y
p l a n s f o r m a j o r e ve n t s w h i c h c o u l d r e s u l t i n l o s s o f
s e r vi c e o r u n wh o l e s o m e w a t e r .
Risk classification: Significant
01 Nov 2015
F o r 3 d a ys
(BRL)
D i a l H i l l s e r vi c e
r e s e r vo i r ,
C l e ve d o n ,
Somerset
16,600
Bristol Water Plc action:

R e m o ve d s e r vi c e r e s e r v o i r f r o m s u p p l y.

Sampled affected area.

Repaired points of ingress.
Mi c r o b i o l o g i c a l
contamination.
DWI comments and findings:

Inadequate communication caused delay in isolating
t h e r e s e r vo i r .

No cause identified.
Risk classification: Significant
82
Western region
Date and
duration
Area
16 Nov 2015
F o r 4 d a ys
(W S X)
S t r a t f o r d To n y,
W il t s h i r e
Estimate of
population
affected
133
Nature and cause
o f t h e e ve n t
Main actions and findings from the Inspectorate
i n ve s t i g a t i o n
Mi c r o b i o l o g i c a l
contamination
caused by planned
work on the
d i s t r i b u t i o n s ys t e m .
W e s s e x W a t e r S e r vi c e s L t d a c t i o n :

Flushed mains.

I n c r e a s e d c h l o r i n e r e s i d u a l s i n t h e d i s t r i b u t i o n s ys t e m .

I s s u e d a b o i l wa t e r n o t i c e .

Sampled affected area.

Th e c o m p a n y ' s r e s p o n s e t o t h e e ve n t w a s a p p r o p r i a t e
timely and proportional.
DWI comments and findings:

Th e I n s p e c t o r a t e w a s m i n d e d t o r e c o m m e n d t h a t t h e
c o m p a n y i m p r o ve t u r n o v e r a n d c h l o r i n e r e s i d u a l s , b u t
noted that appropriate steps had already been taken.
Risk classification: Significant
09 Dec 2015
F o r 1 0 d a ys
( SW T)
Ye t t i n g t o n ,
D e vo n
75
Ta s t e a n d o d o u r
due to burst main.
South West Water Ltd action:

P R V i n s t a l l a t i o n a n d r e v a l vi n g ,

Sharing of learning across operational management.
DWI comments and findings:

Inadequate procedures.

Did not keep customers informed.
Risk classification: Significant
No te : A c om p le t e ta b l e of e ve nts in En g l an d a n d W ales in 2 0 15 c a n b e f o u nd o n t he DW I webs i te ( ww w. d wi .d ef ra. g o v. uk ) .
It is n am ed Sig nif ic an t d rin ki ng w at e r ev e n ts in E ngl an d and W a le s 2 01 5 .pdf .
83
Drinking water 2015
Annex 4
Planned drinking water quality improvements
Company
Parameter,
h a z a r d o r d r i ve r
Site
Due for
completion*
Status*
Legal
Instrument
BRL
Cryptosporidium
Barrow
30-Sep-16
Ongoing
Notice
BRL
Deterioration of
raw water
q u a l i t y, i r o n ,
taste and odour,
nitrite,
ammonium,
arsenic, copper
lead, manganese
Cheddar
30-Apr-21
Ongoing
Notice
BRL
Iron
Tr u n k m a i n s –
consumer
acceptability
3 1 - Ma r - 1 5
D e l a ye d
Undertaking
BRL
Lead
Lead Strategy
3 1 - Ma r - 2 0
Ongoing
Notice
BRL
Me t a l d e h yd e
Purton and
Littleton
3 1 - Ma r - 2 0
Ongoing
Undertaking
BRL
Pesticides
m e t a l d e h yd e
S t o we y
3 1 - Ma r - 1 5
Completed
3 1 - Ma r - 1 5
Undertaking
CHO
Nitrate
Cholderton
3 1 - Ma r - 2 0
Ongoing
Notice
S BW
Cryptosporidium
Alderney
31-Dec-18
Ongoing
Notice
S BW
Cryptosporidium
K n a p p Mi l l
21-Dec-18
Ongoing
Notice
S BW
Iron, turbidity
a n d p o l yc yc l i c
aromatic
h yd r o c a r b o n s
Distribution
3 1 - Ma r - 1 5
Completed
3 1 - Ma r - 1 5
Undertaking
SSE
M e t a l d e h yd e
Distribution
s ys t e m
3 1 - Ma r - 2 0
Ongoing
Undertaking
SW T
Lead
A vo n
31-Dec-16
Ongoing
Notice
SW T
Lead
Lead Strategy
3 1 - Ma r - 2 0
Ongoing
Notice
C r o wn h i l l
31-Dec-19
Ongoing
Notice
To t t i f o r d
31-Dec-19
Ongoing
Notice
Ta m a r
31-Dec-19
Ongoing
Notice
College
31-Jul-18
Ongoing
Notice
Northcombe
31-Dec-18
Ongoing
Notice
SW T
SW T
SW T
SW T
SW T
Me t a l d e h yd e ,
coliforms, E.coli,
Cryptosporidium,
trihalomethanes,
taste and odour
Ta s t e , o d o u r a n d
trihalomethanes
Tr i h a l o m e t h a n e s ,
taste and odour,
m e t a l d e h yd e
pesticides
Tr i h a l o m e t h a n e s ,
taste and odour,
m e t a l d e h yd e ,
pesticides
Tr i h a l o m e t h a n e s ,
taste and odour,
m e t a l d e h yd e ,
p r o p y za m i d e ,
pesticides
84
Western region
Company
Parameter,
h a z a r d o r d r i ve r
Site
Due for
completion*
WSX
Cryptosporidium
Bradley Head
3 1 - Ma r - 1 6
WSX
Cryptosporidium
B r i xt o n D e ve r i l l
3 1 - Ma r - 1 5
WSX
Cryptosporidium
Calstone
3 1 - Ma r - 1 6
WSX
Cryptosporidium
Corscombe
30-Sep-15
WSX
Cryptosporidium
Hooke
30-Sep-17
Ongoing
Notice
WSX
Cryptosporidium
Okeford
F i t zp a i n e
3 1 - Ma r - 1 6
D e l a ye d
Notice
WSX
Cryptosporidium
Pitcombe
3 1 - Ma r - 1 6
WSX
Cryptosporidium
S h a p wi c k
3 1 - Ma r - 1 5
WSX
Cryptosporidium
W el l h e a d
31-Sep-17
Ongoing
Notice
WSX
Cryptosporidium
W es t L u l wo r t h
3 1 - Ma r - 1 6
Ongoing
Notice
WSX
Iron, turbidity
and manganese
Tr u n k m a i n s
3 1 - Ma r - 1 5
WSX
Lead
Distribution
3 1 - Ma r - 1 5
WSX
Lead
Lead strategy
3 1 - Ma r - 2 0
Ongoing
Notice
WSX
Me t a l d e h yd e
Durleigh
30-Apr-15
Completed
3 0 - Ma r - 1 5
Undertaking
WSX
Nitrate
S e ve n d i f f e r e n t
treatment works
3 1 - Ma r - 1 8
Ongoing
Undertaking
WSX
Ta s t e a n d o d o u r
Porlock
31-Dec-17
Ongoing
Notice
WSX
Tu r b i d i t y
Alton Pancras
31-Dec-18
Ongoing
Notice
WSX
Tu r b i d i t y
Arn Hill
30-Jun-16
Ongoing
Notice
WSX
Tu r b i d i t y
Bourton
3 1 - Ma r - 1 9
Ongoing
Notice
WSX
Tu r b i d i t y
Burton Road
3 1 - Ma r - 1 8
Ongoing
Notice
WSX
Tu r b i d i t y
Chitterne
3 1 - Ma r - 2 0
Ongoing
Notice
WSX
Tu r b i d i t y
Codford
31-Dec-17
Ongoing
Notice
WSX
Tu r b i d i t y
C o m p t o n D u r vi l l e
30-Sep-18
Ongoing
Notice
WSX
Tu r b i d i t y
Deans Farm
3 1 - Ma r - 1 8
Ongoing
Notice
WSX
Tu r b i d i t y
Friar W addon
30-Jun-17
Ongoing
Notice
WSX
Tu r b i d i t y
Lacock
31-Jan-19
Ongoing
Notice
WSX
Tu r b i d i t y
Litten Cheney
30-Jun-18
Ongoing
Notice
WSX
Tu r b i d i t y
Me r e
31-Dec-18
Ongoing
Notice
85
Status*
Completed
3 1 - Ma r - 1 6
Completed
3 1 - Ma r - 1 5
Completed
3 1 - Ma r - 1 6
Completed
04-Nov-15
Completed
3 1 - Ma r - 1 6
Completed
3 1 - Ma r - 1 5
Completed
3 1 - Ma r - 1 5
Completed
3 1 - Ma r - 1 5
Legal
Instrument
Notice
Notice
Notice
Notice
Notice
Notice
Undertaking
Undertaking
Drinking water 2015
Company
Parameter,
h a z a r d o r d r i ve r
Site
Due for
completion*
Status*
Legal
Instrument
WSX
Tu r b i d i t y
Pole Rue
3 1 - Ma r - 2 0
Ongoing
Notice
WSX
Tu r b i d i t y
S u t t o n P o yn t z
31-Dec-19
Ongoing
Notice
WSX
Tu r b i d i t y
W as h p o o l
3 1 - Ma r - 2 0
Ongoing
Notice
D a t e s u s e d a r e t h o s e f o r t h e c o m p l e t i o n o f t h e a g r e e d p r o g r a m m e o f wo r k . Th e r e i s a
further period of 12 months before a programme is officially closed to ascertain the
benefits of the work to consumers.
Annex 4.1
Delayed programmes
Company
Parameter,
h a z a r d o r d r i ve r
Site
Reason for dela y
BRL
Iron
Tr u n k m a i n s –
consumer
acceptability
WSX
Cryptosporidium
Okeford
F i t zp a i n e
F i n a l t r u n k m a i n r e n o va t i o n d e l a ye d d u e
to street works restrictions resulting in a
f i ve m o n t h d e l a y t o o ve r a l l c o m p l e t i o n .
W or k wa s c o m p l e t e d i n 3 1 / 1 0 / 5 .
W or k s i s n o w i s o l a t e d a n d o u t o f s u p p l y
b u t p h ys i c a l d i s c o n n e c t i o n o f t h e p i p e h a s
b e e n d e l a ye d d u e t o g r o u n d c o n d i t i o n s .
86
Western region
Annex 5
Competition in the water industry
The f ollowing table indicates the ext ent of competition in the water
industr y in England and W ales .
Inset appointments in pla ce in 20 15
Sit e
S ho tt o n P ap er ,
S ho tt o n
Ris s i n gt on ,
B our t on- o n- t h eW ater
B ux t ed C h ic k en ,
Fl ix t o n
W yn yar d , ne ar
W olvis t on
Br ook l a nds , M i lt o n
K e yn es
G re at Bi l l i ng W a y,
Nor th am pt on
Lo n g Cr of t R o a d,
Cor b y
Pr i ors Ha l l , Cor b y
O ak ham N or t h,
O ak ham
B err yf i e lds ,
A yl es b ur y
G re en wi c h
M il l e n ium V i l l ag e
K in gs Cr os s ,
Lo n do n
T he Br i dg e,
Dar tf or d
Me d i a C it y,
S alf ord Q ua ys
Nor wi c h C om m on,
W ym ondh am
Em ers o ns G r e e n,
Br is t o l
L la n i li d Par k ,
S ou th W ales
Ri v ers i de , B ar k i ng
G ra yl i n g we l l,
Ch ic hes t er
Ne wl a n ds ,
W aterlo o v i l le
Far nd o n Ro a d,
Ma rk et
Har b oro u gh
Ap po int ee
A lb i o n W ater
A lb i o n W ater
A ng l i an W ater
Har t le p oo l W ater
In d ep e nd e nt W ater
Ne t wor k s L td
In d ep e nd e nt W ater
Ne t wor k s L td
In d ep e nd e nt W ater
Ne t wor k s L td
In d ep e nd e nt W ater
Ne t wor k s L td
In d ep e nd e nt W ater
Ne t wor k s L td
In d ep e nd e nt W ater
Ne t wor k s L td
In d ep e nd e nt W ater
Ne t wor k s L td
In d ep e nd e nt W ater
Ne t wor k s L td
In d ep e nd e nt W ater
Ne t wor k s L td
P ee l W ater
Ne t wor k s L td
S S E W ater
S S E W ater
S S E W ater
S S E W ater
S S E W ater
S S E W ater
S S E W ater
87
Inc umb ent and r eg io n
D ŵr C ym r u W els h W ater ,
W ales
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
St atu s
S up p l yi n g
wa ter
S up p l yi n g
wa ter
Es s ex an d Suf f o lk W ater,
Ce ntr a l a n d E as t er n r e g io n
Nor th um br ia n W ater,
Nor th er n r e g io n
A ng l i an W ater,
Ce ntr a l a n d E as t er n r e g io n
A ng l i an W ater,
Ce ntr a l a n d E as t er n r e g io n
A ng l i an W ater,
Ce ntr a l a n d E as t er n r e g io n
A ng l i an W ater,
Ce ntr a l a n d E as t er n r e g io n
S e ver n T ren t W ater, C en tr al
an d E as ter n re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
Un i te d Ut i l it i es , N or th ern
reg i o n
A ng l i an W ater
Ce ntr a l a n d E as t er n r e g io n
Br is t o l W ater , W es tern
reg i o n
D ŵr C ym r u W els h W ater,
W ales
Es s ex an d Suf f o lk W ater,
Ce ntr a l a n d E as t er n r e g io n
P orts m ou th W ater, Lo nd o n
an d S o ut h E as t r e gi o n
P orts m ou th W ater, Lo nd o n
an d S o ut h E as t r e gi o n
S e ver n T ren t W ater, C en tr al
an d E as ter n re g i on
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
Drinking water 2015
Sit e
Hi l ls Fa rm La n e,
Hors h am , S ur r e y
P ark V i e ws ,
E ps om
Ap po int ee
S S E W ater
Br om le y C om m on,
Br om le y
G re at W es ter n
P ark , D i dc o t
Ha l e V i l la g e,
T ott en h am
He art of Eas t
G re en wi c h
K en n et Is l an d ,
Re a di n g
K in gs m ere ,
B ic es t er
Ma ri n e W har f ,
De ptf ord
Ne w S ou t h
Q u art er, Cr o yd o n
Ni n e E lm s ,
Lo n do n
Br e wer y S q ua r e ,
Dorc h es t er
O l d S ar um ,
S al is b ur y
Mo D T id wo r t h
ne ar An d o ver
S S E W ater
S S E W ater
S S E W ater
S S E W ater
S S E W ater
S S E W ater
S S E W ater
S S E W ater
S S E W ater
S S E W ater
S S E W ate r
S S E W ater
V eo l i a W ater
Pr oj ec ts
Inc umb ent and r eg io n
S ou th er n W ater, L on d on an d
S ou th E as t re g i on
S ut to n a nd E as t S urr e y
W ater, Lo n do n a n d S o ut h
E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
T ham es W ater, L o nd o n a nd
S ou th E as t re g i on
W es s ex W ater,
W es tern r e gi o n
W es s ex W ater,
W es tern r e gi o n
W es s ex W ater,
W es tern r e gi o n
St atu s
S up p l yi n g
wa ter
S up p l yi n g
wa ter
Inc umb ent and r eg io n
Cam br id g e W ater, Ce n tra l
an d E as ter n re g i on
Es s ex an d Suf f o lk W ater,
Ce ntr a l a n d E as t er n r e g io n
Af f in i t y W ater a n d S o u th er n
W ater, Lo n do n a n d S o ut h
E as t r e g i on
S e ver n T ren t W ater, C en tr al
an d E as ter n re g i on
St atu s
A pp o i ntm en t
gra n te d
A pp o i ntm en t
gra n te d
A pp o i ntm en t
gra n te d
W es s ex W ater,
W es tern r e gi o n
A pp o i ntm en t
gra n te d
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
S up p l yi n g
wa ter
New inset appointments in 2015
Sit e
Nor ths t o we,
Cam br id g e
W oods M e ad o w.
O u lt o n, S uf f o lk
Ma rt e ll o L ak es ,
H yt he
Ap po int ee
A ng l i an W ater
Ca d le y H i l l,
S wa d l inc ot e
S ou th
St af f or ds h ir e
W ater
S S E W ater
Cas t le W a y, O l d
S arum
A ng l i an W ater
In d ep e nd e nt W ater
Ne t wor k s L td
88
A pp o i ntm en t
gra n te d
Western region
Annex 6
Water company indices
Key
Bournemouth W ater (SBW )
Bristol W ater (BRL)
Cholderton and District W ater (CHO)
South W est W ater (SW T)
SSE W ater (SSE)
Veolia W ater Projects (VW P)
W essex W ater (W SX)
Industr y aver age (Industr y)
Overall drinking w ater index
89
Drinking water 2015
Process control index
Disinfection index
90
Western region
Distribution index
Reservoir integrit y
91
Drinking water 2015
Annex 7
Glossary and description of standards
These def init ion s will assist the understanding of the report where
technical terms have been used.
µg/ l
m ic rogr am pe r l itr e (o ne m il l i on t h of a gram
per l itr e).
1, 2- D i chl or oet ha ne
is a s o l v en t t ha t m a y b e f o u nd in gro u nd wa t e r i n
th e v ic i n it y of i nd us tr i a l s it es . W h ere n ec es s ar y
it c an b e rem o ve d b y s pec i a l wa t er tre a tm ent .
A E ur op e a n he a lt h - b a s ed s t a nd ar d of
3μ g/ l a p pl i es .
Ac r yl am id e
E uro p ea n h e al t h - b as e d s ta n dar d . A c h em ic a l
wh ic h is n ot norm a l l y f ou n d i n dr i nk in g wa t er . I t
is pr od uc e d i n th e m a nuf ac t ure of
po l ya c r yl am i d es t h at a re oc c as i o n al l y us e d i n
wa ter t re atm e nt. I ts pr es e nc e i n dr i nk in g wa t er is
l im it e d b y c on tro l of t h e pr od uc t s pec if ic a t io n .
St a nd ar d is 0 . 1µ g/ l.
Ae s th eti c
as s oc i at e d wi t h th e s e ns es of t as t e, s m el l
an d s i g ht .
Ag g re s siv e
a term us e d to in d ic at e th a t t h e wa t er h as a
te n de nc y t o d is s o l v e c op p er ( a nd ot he r m et a ls )
f r om the in n er s urf ac e of a p i pe or wa ter f i tt i ng
s uc h as a ta p .
Al k a li
a s o lu t io n c o nt a i n in g a n ex c es s of f re e h yd ro x yl
i ons , wi t h a p H gr ea te r t ha n s e v e n.
Al u min iu m
oc c urs na tu ra l l y i n s o m e s ourc e wat ers . I t i s
r em ov e d f rom dr i nk in g wat er b y c o n v en t io n a l
wa ter t r e atm e nt (c o a g u la t io n a nd f i l tra t io n) .
A lum i n ium s u l ph a te a n d p ol ya l um i n ium c h l or i de
m a y be us e d as wat er tre atm e nt c h em ic a ls a t
s om e wat er tr e atm en t work s . A n a ti o na l s t a n dar d
of 2 0 0μ g/ l a p pl i es .
Am m oni um
s a lts ar e n at ur a ll y p re s en t i n tr ac e am o un ts i n
m os t wat ers . T he ir pre s enc e m ig ht i n d ic a te
c on t am in at i on of s a n it ar y s i gn if ic a nc e a nd t h e y
i nt erf er e wi t h th e o p er at i on of t he dis i nf ec ti o n
pr oc es s . A n i nd ic at or par am et er wi t h a g u id e
v a lu e of 0. 5m g/ l.
92
Western region
An a l yti c al qu al it y co nt ro l
( AQ C)
proc e d ures us e d to en s ure t h at la b ora t or y
an a l ys is m et h ods ar e perf orm in g c orr ec t l y.
An ti mon y
is r ar e l y f o u nd in dr ink i ng wat er .
T rac e am ou nts c a n b e d er i ve d f rom br as s ta p
f itt i n gs an d s o l de rs . A E uro p ea n h e al t h - b as e d
s ta n dar d of 5 μ g/ l a p p li es .
Aq ui fe r
wa ter - c o nt a i ni n g u nd e rgr ou n d s tra t a.
Ar s e ni c
oc c urs na tu ra l l y i n o n l y a f e w s ourc es of
gro u n d wat er. S pec if ic wa ter t re atm e nt is r eq u ire d
to rem o v e it . A Eur o p e an he a lt h - bas e d s ta n d ard
of 1 0μ g /l ap p l ies .
Benz en e
is pr es e n t i n p e tr o l. I t is n ot f o un d i n dr i nk in g
wa ter , b ut it c a n m i gr a te t hr ou g h u nd er gro u n d
p las t ic wa te r p ip es if p etr o l is s p i lt i n t h e v ic i n it y.
A E ur op e a n he a lt h - b a s ed s t a nd ar d of 1 μ g/ l
ap p l ies . S om e bo tt l e d wa ters an d s of t dr i nk s
wh ic h i nc lu d e s o di um be n zo a t e as a n i ngr e d i en t
ha v e b e en r ep ort e d as c o nt a i ni n g b en ze n e .
Benz o(a ) p yr en e
is o ne of s e v er a l c om pou n ds k n o wn as p o l yc yc l i c
arom at ic h yd r oc arb o ns (P A Hs ) . T h ei r s ourc e i n
dr ink i n g wa ter is as a res u l t of de te ri or at i o n of
c oa l t ar, wh ic h m an y y ears ag o wa s us e d t o l i ne
wa ter pi p es . D u e to ex te ns i ve wa ter m ai ns
ref ur b is hm en t a nd r en e wa l i t is n o w r are t o
de t ec t t h is s ubs t anc e i n dr ink i n g wa t er.
A E ur op e a n he a lt h - b a s ed s t a nd ar d of
0. 0 1μ g/ l a pp l i es .
Bo ron
i n s urf ac e wa t er s ou rc es c om es f rom i n dus tr i a l
d is c h ar ges or f rom d et erg e nts in tr e at e d s e wag e
ef f lu e nts . T h e v er y l o w c onc e ntr at i o ns f o u n d i n
s om e dr i nk in g wat ers are no t a c o nc ern t o
pu b l ic h ea l th . A Eur o p ea n h e al t h - b as ed s t a n dar d
of 1m g/ l a p p li es .
Br om ate
c an be f orm ed d ur i ng d is i nf ec t io n of dr ink i n g
wa ter t hr o ug h a re ac ti on be t we en n a tur a l l y
oc c ur ri n g br om id e a nd s tr on g ox i d an ts ( us ua l l y
o zo n e). I t m a y b e ge n era t ed in t h e m an uf ac t ure
of s o d i um h yp o c hl or i te d is i nf ec t a nt .
Ex c ep t io n a ll y, gr o un d wa ter c an b e c o n tam in at e d
wi t h brom at e , r e le as e d f rom a n i n dus tr i al s it e.
A E ur op e a n he a lt h - b a s ed s t a nd ar d of
10 μg / l a pp l i es .
Bul k su ppl y
wa ter s up p l ie d i n b u lk , us u al l y i n tr e at e d f or m ,
f rom on e wa te r c om pa n y to an ot h er.
93
Drinking water 2015
Cad mi um
is r ar e l y d et ec t e d i n dr i nk in g wa t er a nd tr ac e
am oun ts ar e us ua l l y d ue t o d is s o lu t io n of
im pur it i es f r om pl um bi ng f i tt i ngs . A Eur o p ea n
he a lt h- b as e d s t an d ard of 5 μ g/ l a p p li es .
Cat ch me nt
wh e n us e d i n c o n nec t i on wi th wa ter , th e
c atc hm ent is th e ar e a dra i n ed b y a r i v er or
wa ter bo d y.
Chlo r am in at i on
th e pr oc es s of g e ner a t i ng a c hl or am in e
d is i nf ec ta n t r es id u a l i n wa t er l ea v i n g a
tr e atm e nt work s .
Chlo r am in e
a s u bs t anc e f orm ed b y a re ac ti o n b et we e n
c h lor i n e an d am m oni a, us e d as a d is inf ec t an t i n
d is tr i bu t io n s ys t em s b ec a us e of its lo n g - las t i ng
pr o p ert i es c om par e d t o c h lor i n e.
Chlo r id e
is a c om po n en t of c om m on s a l t. I t m a y oc c ur i n
wa ter na tu ra l l y, bu t i t m a y als o b e pr es en t d ue
to loc a l us e of d e - ic i n g s a lt or s al i n e i ntr us i on .
A n i nd ic at or p ar am ete r wit h a g u i de v al u e
of 2 5 0m g/l .
Chlo r in e r es idu al
th e s m a ll am oun t of c h l ori n e or c h l or am in es
pr es e nt in dri nk i ng wa ter t o m a in t ai n i ts q ua l it y
as i t pas s es t hro u g h t he wa ter c om p an y’ s
ne t work of p i pes a n d h ous e ho l d p l um bi ng .
Ch rom ium
is n ot pr es e nt i n dr i nk i ng wa ter . A Eur o pe a n
he a lt h- b as e d s t an d ard of 5 0 μ g/ l a pp l i es .
Clo st ri diu m p e rf rin ge ns
is a s p or e - f orm in g b ac ter i um th at is pr es e n t i n
th e g ut of wa rm - bl oo d ed an im als . T h e s p or e s c a n
s ur v i ve d is i nf ec ti o n. T he pres e nc e of s p or es i n
dr ink i n g wa ter in d ic at e s h is tor ic c o nt am in a ti o n
th at r eq u ir es i n ves t ig a ti o n. T he s t a nd ar d is
0 p er 10 0m l.
Coa gul at ion
a pr oc es s em p lo ye d d ur in g dr i n k in g wa t er
tr e atm e nt t o as s is t wi t h th e rem o va l of
par t ic u l a te m att er.
Col ifo rm b act e ri a
ar e wi d e l y d is tr i bu t ed i n th e e n v iro nm en t of t en
as a r es u lt of h um an o r a n im al ac t i vi t y, bu t s om e
gr o w o n p l an t m at ter . T hei r pres e nc e i n a w at er
s up p l y i n dic a tes a ne e d to in v es ti g at e t he
i nt egr i t y of t h e wa t er s up p l y s ys t em .
T he s ta n dar d is 0 pe r 10 0m l.
94
Western region
Colo n y c ount s
are ge n era l t ec hn i q ue s f or d et ec t i ng a wi d e
ran g e of bac t eri a , th e t yp e s a nd num bers be i ng
de p en d en t o n th e c o n d it i ons of t he t es t .
T hes e c o u nts , if d on e reg u l ar l y, c a n h e lp t o
i nf orm wa ter m an ag em en t, bu t th e y h a v e no
d irec t h ea l th s ig n if ic a nc e . T h e s t an d ard is ‘ no
ab n orm al c h a ng e ’.
Colo ur
oc c urs na tu ra l l y i n u p l an d wat er s o urc es .
It is r em ov ed b y c on v e nt i on a l wa t er tr ea tm en t.
A n at i on a l s t an d a r d of 2 0m g/ l on t h e
P la t in um /C ob a lt ( Pt /C o) s c a le ap p l ies .
Com mun ic at ion pip e
th e c o nn ec ti o n f r om th e wa t er m ai n t o th e
c ons um er’s pro p ert y b ou n da r y.
Comp li an c e a ss e ss m ent
a c om par is on m ad e b y t he I ns pec t ora te of d a ta
ga t her e d b y wa t er c om pa n i es ag a i n s t s t a nd ar ds
an d o th er re g u la to r y r eq u ir em ents .
Comp ound
a c om po un d c o ns is ts of t wo or m ore e l em en ts
i n c hem ic a l c om bi na t i on .
Con ce s sio na r y sup pl ie s
h is t or ic a l f re e s up p l i e s of wa t er f or a
ho us eh o l der , es ta b l is h ed wh en a c om pa n y
wa nt e d to la y m a i ns a c ros s l an d a n d th e
l an d o wne r m ig h t agr e e , s ubj ec t t o a p erm is s i on ,
to t ak e a s u pp l y of wa t er f r om th e m ai n .
Condu ct iv it y
is a n o n - s p ec if ic m eas ure of t he am oun t of
na t ura l d is s o l ve d i n or ga n ic s u bs t a nc es in
s ourc e wat ers . A n i nd i c at or p ar am eter wi th
a g ui d e v a lu e of 2, 5 0 0 µS /c m .
Cont ac t t an k
a ta nk , norm a l l y s it u at ed on a tr e atm en t wo r k s
s it e , wh ic h f orm s p ar t of t h e d is i nf ec t io n pr o c es s .
A d is inf ec t a nt c h em ic a l ( n orm al l y c h l or in e) is
dos e d i nt o t he wat er a s i t f lo ws i nt o t he t a nk .
T he pe ri o d of t im e th a t t h e wa t er tak es t o f lo w
thr o ug h t he t a nk a l lo w s s uf f ic i en t ‘c on t ac t ’ t i m e
f or t h e c hem ic a l to k il l , or d eac t i va te , a n y
v ir us es o r pa t ho g en ic org a n is m s th at m a y b e
pres e nt in t h e wa t er.
Copp e r
i n dr ink i n g wa ter c om es m os tl y f r om c o pp er
p ip es a nd f i tt i n gs in h ous e ho l ds . I n g e ner a l,
wa ter s ourc es ar e n ot ag gr es s i ve t o war ds
c op p er, b u t pr ob l em s v er y oc c as i o n al l y oc c u r o n
ne w h ous i n g es t at es . T hes e ‘b l u e wa ter ’ e ve nts
c an be a v o i de d b y g o o d p lum b in g pr ac t ic es .
A E ur op e a n he a lt h - b a s ed s t a nd ar d of
2m g/l ap p l ies .
95
Drinking water 2015
Cr ypt osp or id ium
is a p ar as it e th a t c aus es s e v ere g as tro e nt er i tis
an d c a n s ur v i v e d is inf ec t i on . It is r em ov e d f r om
wa ter b y c on v e nt i o na l proc es s es f o r r em ov i n g
par t ic u l a te m ater i a l, a nd is i nac t i va t ed b y
u ltr a v io l et l ig ht . I n th e U K, c on t in u ous m on i t or in g
is u nd er tak e n at work s c l as s if i e d b y th e c om pa n y
as b ei n g at s ig n if ic a nt ris k .
C yan id e
is n ot pr es e nt i n dr i nk i ng wa ter . A Eur o pe a n
he a lt h- b as e d s t an d ard of 5 0 μ g/ l a pp l i es .
De ad l eg
r ef ers t o a p i ec e of p i p in g wh ic h is s t o p pe d of f at
on e e n d, b ut is c o nn ec te d t o t h e s u pp l y a t t h e
ot h er en d a n d c a n r es u lt i n s t ag n an t wa t er i n
th e p i pe wo rk .
Di st rib utio n s yst em s
a wa t er c om pa n y’s ne t work of m a ins , p i pes ,
pum p in g s t at i ons an d s er v ic e r es er v o irs t hro ug h
wh ic h tre a te d wat er is c on v e ye d t o c o ns um ers .
Dr in kin g W at er D i re c t iv e
Co u nc i l D ir ec t i v e 9 8/ 8 3/ E C Dec em ber 1 9 98 –
s et t in g o ut dr i nk i ng wa ter s t a nd ar ds to be
ap p l ie d i n m em ber s t a tes .
Dr in kin g w at e r st a nd ar ds
th e pr es c r ib e d c o nc e n tra t io ns or va l u es l is t e d
i n r eg u l at i ons .
Enfo r c em ent a ct ion
th e m ea ns , as s et ou t i n th e W ater Ac t 1 9 89
an d c o ns ol i d at e d i nt o th e W ater I n dus tr y Ac t
19 9 1, b y wh i c h th e S e c ret ar y of S ta te r eq u ir es
a wa t er c om pa n y to c o m pl y wi t h c e rt a in
r eg u l at or y re q uir em en t s .
Ent e ro co cc i
s ee Es c h er ic h ia c o l i .
Env i ro nm ent Ag en c y
th e E n v ir onm en t A g en c y is r es p o ns ib l e f or
m aint a i n in g a nd im pro v i ng t h e qu a l it y of f r es h,
m arin e, s urf ac e an d u nd er gr ou n d wa t er i n
E ng l a nd . Na t ura l R es o urc es W ales i s t h e
eq u i v al e nt b o d y i n W ales .
Ep ic hlo ro h yd r in
c an be f o un d i n tr ac e am oun ts i n p o l yam i ne
wa ter t re atm e nt c h em ic a ls . Its pres e nc e i n
dr ink i n g wa ter is l im it e d b y c o ntr o l of t h e pr o duc t
s pec if ic a t io n. A E ur op ea n h e al t h - b as ed s t a n dar d
of 0 . 1μ g/ l a pp l i es .
Ep id em iolo g y
a pr oc es s of s t ud yi n g th e d is tr i b ut i on of c as es of
d is e as e wi t hi n a p o p ul at i on in r e la t io n t o
ex p os ur e t o p os s i bl e s ourc es of th e i nf ec t io n ,
wi t h a v i e w t o es ta b l is h in g t he ac t ua l s o urc e of
th e i nf ec ti o n.
96
Western region
E sc he ri ch i a col i an d
Ent e ro co cc i
are bac te ri a pr es en t i n t he gu t of warm - b lo o d ed
an im a ls . T h e y s h o ul d no t b e pr es e n t i n dr ink i ng
wa ter an d, if p res e nt , i m m edia t e ac t i on is
req u ir ed t o i d en t if y a n d r em ov e a n y s o urc e o f
f aec al c on tam i na t io n t ha t is f o un d. T he s t a n dar d
is 0 p er 1 0 0m l.
Ev e nt
wa ter c om pan i es h a v e t o i nf orm th e I ns p ec to rat e
ab o ut oc c as i ons wh en wa ter qu a l it y or
s uf f ic i e nc y is af f ec t e d or wh e n p ub l ic c o nf i d e nc e
i n dr ink i n g wa ter qu a l i t y m a y b e im pac t e d. T he
Ins p ec t ora t e r ef er t o t hes e i ns ta nc es as ‘ E v en ts ’.
Filt r ati on
wh er e wa t er is p as s e d t hro u gh a p oro us m at er ia l
(e. g. s an d) t o r em ov e s us p e nd e d p art ic u la te
m atter .
Fluo ri de
oc c urs na tu ra l l y i n m a n y wa t er s ou rc es ,
es p ec i al l y g ro u nd wa t e r. It c a n no t b e r em ov e d b y
c on v e nt i on a l wa t er tr e atm en t s o h i gh le v e l s m us t
be r ed uc ed b y b le n di n g wi t h a no th er lo w f lu o ri de
wa ter s ourc e . S om e wat er c om pa n ies are
req u ir ed b y th e l oc a l h ea l th au th or i t y to
f lu or id at e wat er s u p p li es as a pr ot ec ti o n a ga i ns t
to ot h d ec a y. T he dr i nk i ng wat er s t a nd ar d
ens ur es l e v els are s af e i n e it h er c irc um s tan c e.
Fl uo ri d at i on of wat er i s a D e par tm ent of H ea lt h
po l ic y. A E ur o pe a n he a lt h - b as e d s ta n dar d of
1. 5m g/ l ap p l i es .
G eo sm in
a s u bs t anc e pr o duc e d b y a v ar i et y of n at ur al l y
oc c ur ri n g m ic r ob es , n orm al l y i n s urf ac e wat ers
wh ic h g i ves r is e to a c har ac ter is t ic ‘ ear t h y’ o r
‘m us t y’ tas te or o do ur .
G r anu la r a ct iv at ed c a rbon
an ads or be n t f i l tra t io n m edi um us ed t o rem o v e
trac e or g an ic c om po u n ds f rom wat er .
G ro s s alp ha /g ro ss b e t a
rad i o ac t i v it y i n r a w wa ter c a n or i g in a te f rom
na t ura l s u bs ta nc es or f r om a s p ec if ic p o i nt
em is s i o n. W ater c om pan i es ar e r e qu ir e d to
s c ree n f or r a d io n uc li d es th a t em it e it h er a lp ha or
be t a par t ic les . If s uc h s c ree n i ng ex c e e d s gu i de
v a lu es ( gr os s a l ph a 0 . 1 Bq / l, gr os s b et a 1 .0 B q/ l)
th e n f u l l er a na l ys is f or s p ec if ic ra d i on uc l id e s is
c arr ie d o ut t o d et erm i ne t h e or i gi n .
G rou ndw at er
wa ter f rom a q uif ers or o th er u n der gr o un d
s ourc es .
97
Drinking water 2015
H yd ro ge n Ion
(pH)
g i ves a n i n d ic a t io n of th e d egr e e of ac id i t y o f th e
wa ter . A pH of 7 is n e utr a l; va l u es b el o w 7 a re
ac id ic a n d v a lu es a b o v e 7 ar e a lk al i n e.
A l o w pH wat er m a y re s u lt i n p i pe c orros i o n.
T his is c orr ec te d b y a dd i n g an alk a l i d ur in g
wa ter t re atm e nt. A s p e c if ic at i o n of b e t wee n
6. 5 a nd 9. 5 a pp l i es .
Imp rov em ent pr og ra mm es
wa ter c om pan y im pr o v em ent work s , th es e ar e
l eg a l l y b in d i ng o n t he c om pan y a n d e ac h
pr o gr am m e wi l l r em ed y a n ac tu a l or p ot e nt i a l
br e ac h of a dr ink i n g w at er s t an d ard wi th i n a
s pec if ie d t im e p er i od .
Indi c ato r or ga ni sm
an org a n is m wh ic h i nd ic at es th e pr es enc e of
c on t am in at i on a n d h en c e th e p os s ib l e pr es en c e
of p a th o ge ns .
Indi c ato r pa r am et er
s om eth i n g t h at is m ea s ure d t o c h ec k th a t
c on tr ol m eas ur es , s uc h as wa t er tr ea tm ent ,
ar e work i ng ef f ec t i ve l y.
Info rm at ion Le t t e r
f orm al gu i d anc e t o wa t er c om pa n ies g i v e n
b y th e I ns p ec tor at e a n d p ub l is he d o n th e
Ins p ec t ora t e ’s we bs it e a t ht tp :/ / ww w. d wi .g o v .uk
Ins pe cto r at e
T he Dr ink i ng W ater I n s pec t ora te .
Iro n
is pr es e n t n at ura l l y i n m an y wa t er s o urc es .
It is r em ov ed b y wa te r tr ea tm en t. S om e ir on
c om pou n ds ar e us ed a s wat er tr ea tm ent
c hem ic a ls . H o we v er, t he c om m ones t s o u rc e
of iro n i n dr i nk in g wa t er is c orr os i on of ir o n
wa ter m ai ns . A n at i on a l s ta n dar d of
20 0μ g /l ap p l ies .
Le ad
v er y oc c as i o n al l y oc c u rs n at ur a l l y i n r a w wa t ers ,
bu t t he us u a l r e as o n f or i ts pr es e nc e i n dr in k ing
wa ter is p l um bin g in o l der pro p ert i es . If th e wa ter
s up p l y h as a t en d enc y t o d is s o l v e l e ad t h en
wa ter c om pan i es tr ea t t he wa ter t o re d uc e
c ons um er ex p os ur e. T he perm an e nt r em ed y is
f or h o us e h o ld ers t o r e m ove l e a d p ip es a nd
f itt i n gs . T he Eur o pe a n h e al t h - b as ed s t a nd ar d is
10 μg / l.
3
m /d
c ub ic m etr es per da y.
M angan es e
is pr es e n t n at ura l l y i n m an y s o urc es a nd is
us u a l l y r em ov e d d ur in g tre a tm ent . A n at i o na l
s ta n dar d of 5 0 μ g/ l a pp l ies .
98
Western region
M ean z on a l com pl ia n ce
pe rc ent ag e
a m eas ur e of c om pl ia n c e wi t h dr i nk in g wa t er
s ta n dar ds i n tro d uc e d b y th e I ns p ec to r at e in
20 0 4.
M ercu r y
is n ot f o un d i n s o urc e s of dr ink i n g wa t er.
A E ur op e a n he a lt h - b a s ed s t a nd ar d of
1μ g/ l a p pl i es .
M ethyli so bo rn eol ( M IB)
a n at ura l s ubs ta nc e pr od uc ed b y th e gr o wt h of
a lg a e, n orm al l y i n s urf ac e wa ters wh ic h g i ve s
ris e to a c har ac ter is t ic ‘ e art h y’ or ‘m us t y’ t as te or
od o ur. I t is d et ec te d b y t h e m eth o d f o r as s e s s i ng
tas te an d o do ur .
mg/ l
m ill i gr am per li tr e ( o n e th o us a n dt h of a gr a m
per l itr e).
M icrob iol ogi c al
as s oc i at e d wi t h th e s t ud y of m ic ro bes .
M l/d
m ega l itr e p er d a y ( o ne M l /d is eq u i v a le nt t o
3
1, 0 00 m /d , 1 m i l li o n l i tres /d or to 22 0, 0 00
ga l l ons / d).
Ni ck e l
oc c urs na tu ra l l y i n s o m e gro u nd wa t er a nd wher e
nec es s ar y s p ec ia l tr e a tm ent c a n b e i ns t a l le d t o
rem ov e i t. An ot h er s o u rc e of nic k e l i n dr i nk in g
wa ter is th e c o at i n gs o n m od er n ta ps a n d ot h er
p lum b in g f it t in gs . A E u rop e a n he a lt h - b as e d
s ta n dar d of 2 0 μ g/ l a pp l ies .
Nit r ate
oc c urs na tu ra l l y i n a l l s ourc e wat ers a l th o ug h
h ig h er c o nc e ntr a ti o ns te n d to oc c ur wh ere
f ert il is ers ar e us e d on th e l a nd . N itr at e c a n b e
rem ov e d b y i o n ex c h a ng e wat er tr ea tm en t or
thr o ug h b l en d i ng wi th ot h er l o w n i tra t e s ou rc es .
A E ur op e a n he a lt h - b a s ed s t a nd ar d of
50m g/ l a p p li es .
Nit rit e
is s om et im es p ro d uc e d as a b y - pr od uc t wh e n
c h lor am in e is us e d as th e es s en t ia l r es i d ua l
d is i nf ec ta n t i n a p ub l ic w at er s u pp l y.
Ch l or am ine is th e res i du a l d is inf ec t an t of c h o ic e
i n l arg e d is tri b ut i o ns s ys t em s b ec a us e i t is m ore
s ta b le an d l o ng - l as t i n g. C ar ef u l o per at i o n of t he
d is i nf ec t io n pr oc es s e ns ur es l e v e ls of ni tr it e ar e
k ept b e lo w th e s t an d ar d. A E uro p ea n h e a lt hbas e d s ta n da rd of 0 .5 m g/l a pp l i es .
Noti c e
an ins tr uc t i on s er ve d b y th e S ec r et ar y of S t at e
(i n th e c as e of wa ter s up p l ies , t he C h ief
Ins p ec t or of W ater) re qu ir i n g s pec if ic ac t i on s t o
be t ak en b y th e r ec i p i en t wi t h in a s pec if ie d
tim es c a l e.
99
Drinking water 2015
NT U
ne p he l om etr ic tu rb i d it y u n i t – t h e u ni t of
m eas ur em ent f or t urb i d it y i n wat er
O dou r
c an aris e as a c ons e q ue nc e of na tu ra l pr oc e s s es
i n s urf ac e wa t ers , p ar t ic ul ar l y b et we e n l at e
s pr in g a n d ear l y a u tu m n. W ater tr e atm en t w it h
ac t i v at e d c ar bo n or o z on e wi l l r em ov e n at ur a l
s ubs t anc es c a us in g t a s te . T h e s ta n da rd r el a tes
to t h e e va l u at i ons of a p a ne l of p eo p le as s es s i ng
s am pl es i n th e l a bo ra t or y.
O fw at
th e wa t er i n dus tr y’ s ec on om ic r e gu l at or .
O oc ys t
th e r es is t a nt f orm i n w h ic h Cry pt os p ori d i um
oc c urs in t h e e n v ir o nm en t, an d wh ic h is c ap a b le
of c a us i ng inf ec t io n .
O rg ano l ept i c
c har ac ter is t ic s of a s u bs t a nc e as de tec t ed b y o u r
s ens es , f or ex am pl e t a s te , o do ur or c o l o ur.
O z one p ro ce s s ( oz on at i on)
th e a pp l ic at i on of o zo ne gas in d ri nk i ng
wa ter t re atm e nt.
P ar am et e rs
th e s u bs t a nc es , or ga n i s m s and p ro p ert i es l is te d
i n Sc he d u le 2 an d R eg u la t io n 3 of th e
r eg u l at i ons . P ar am ete r d ef i n it i o ns c an be f o un d
i n th is g l os s a r y.
P athog en
an org a n is m wh ic h c a n i nf ec t hum ans an d
c aus e d is eas e .
PC V
s ee ‘ Pres c r i b ed c onc e ntr at i o n or v a l ue ’ .
P er iod i c rev iew
th e ec on om ic r e gu l at o r’s pr oc es s of s e tt i n g
wa ter pr ic es .
P est i cid e s
an y f u ng ic i de , h er bic i d e, ins ec t ic i de or r e la t e d
pr o d uc t ( ex c l u d in g m ed ic i n es ) us ed f or t he
c on tr ol of p es ts or d is eas es .
P est i cid e s – or gan oc hlo r in e
com poun ds ( ald ri n, d ie ld rin ,
hept a chl or , he pt a ch l or
epo xi de)
ar e no lo n ger us e d i n t he U K b ec a us e t h e y ar e
pers is te n t i n th e e n v ir onm en t. T h e y ar e no t f ou n d
i n dr ink i n g wa ter . A E uro p e an c h em ic a l s t a n dar d
of 0 . 03 μg / l f or e ac h c o m poun d a p p li es .
100
Western region
P est i cid e s – ot h er t h an
org ano ch lo ri ne c omp ound s
is a d i v ers e an d l ar g e gro u p of org a n ic
c om pou n ds us ed as w ee d k il l ers , ins ec tic i d e s
an d f un g ic id es . M an y wa ter s ourc es c o nt a i n
trac es of on e or m ore pes t ic id es as a r es u l t of
bo t h agr ic u lt ur a l a nd n on - a gr ic u l tu ra l us es ,
m ain l y o n c r o ps an d f o r wee d c o nt ro l o n
h ig h wa ys a n d i n g ard e ns . W here n ee d ed , wa ter
c om pan i es h a v e i ns t a l l ed wat er tr e atm en t
(ac t i v at e d c ar bo n a n d o zo n e) s o t ha t p es t ic i des
are no t f o u n d i n dr ink i ng wa ter . W ater c om p an i es
m us t t es t f or th os e p e s ti c i d es us e d wi de l y i n
th e ir ar ea of s u p pl y. P es t ic i de m on it or in g t h us
v ar ies ac c or d in g t o r is k . A E ur op e an c hem ic a l
s ta n dar d of 0. 1 μ g /l f or e ac h i nd i v i du a l s u bs t anc e
an d 0 .5 μg / l f o r t h e t ot a l of a l l p es t ic i des ap p l ies .
Pho sp hat e do sin g
tre atm e nt of wa t er th a t r es u l ts i n a pr ot ec ti v e
f ilm b u il d i ng up o n t he i ns i de of p i pes m in im i s i ng
th e l ik e li h oo d of l e ad be i n g pr es e nt in dr ink i ng
wa ter s up p l ie d t hr ou g h l ea d p i pes .
Pl umb oso lv e nc y
th e t en d enc y f or l e ad t o d is s o l v e i n wa t er.
Po l yc yc li c a ro mat i c
h yd ro c ar bon s
(P AH s )
is a gr o up nam e f or s e v era l s u bs ta nc es pr es en t
i n pe tr ol e um - bas ed pr od uc ts s uc h as c oa l t a r.
(s ee B en zo ( a)p yr e n e l i s te d a bo v e f or m or e
i nf orm at io n) . A E ur op e an he a lt h - bas e d
s ta n dar d of 0. 1 μ g /l f or t he s um of a l l th e
s ubs t anc es a pp l i es .
Pow de r ed a ct iv at ed c ar bon
(P AC )
po wd er e d ac t i v at e d c a rbo n is em pl o ye d i n
tre atm e nt pr oc es s es t o r em ov e p o l lu ta n ts .
P re s c rib ed c onc en t r a t ion o r
v alu e ( P C V)
th e n um eric a l v a lu e as s i gn e d to d ri nk i ng wat er
s ta n dar ds d ef i n in g t he m ax im al or m in im al le ga l
c onc e ntr at i o n or v a l ue of a p aram et er .
P riv ate s upp l y
wa ter s up p l ie d f or h u m an c o ns um pti o n or f o od
pro d uc t i o n wh ic h is n o t pro v i d ed b y a wa t er
un d ert ak er or l ic e ns e d wat er s u pp l i er.
P rotoz oan p a ra si t e s
a s i ng l e c e l l or ga n is m th at c an o n l y s ur v i v e b y
i nf ec t i ng a hos t, f or ex am pl e Cry p t os p or i di u m .
Pub li c su ppl y
wa ter s up p l ie d b y a c o m pan y l ic ens e d f or
th at pur p os e .
Raw w at e r
wa ter pr ior t o rec e i v in g tre a tm ent f or t he p ur pos e
of dr i nk i ng .
101
Drinking water 2015
Reg ul ati on s
T he W ater S u pp l y (W ater Q ua l it y) Re g ul a ti o n s
20 0 0 ( E n gl a nd ) an d s u bs e q ue n t am en dm ents ,
an d t he W ater S u pp l y (W ater Q u a l it y)
Re g ul a ti o ns 2 01 0 (W ales ).
Re me di al a ct ion
ac t i on t ak en t o im pr o v e a s i tu a ti o n.
Re mot e o pe r at ed v eh ic le
(RO V)
eq u i pm ent f or i ns pec t i ng are as t ha t ar e d if f i c u lt
to ac c es s , f or ex am pl e , i ns i d e ta nk s a n d p ip e s .
Re si du al di si nf e ct ant
th e s m a ll am oun t of c h l ori n e or c h l or am in es
pr es e nt in dri nk i ng wa ter t o m a in t ai n i ts q ua l it y
as i t pas s es t hro u g h t he wa ter c om p an y’ s
ne t work of p i pes a n d h ous e ho l d p l um bi ng .
Ri sk as s es sm ent
a r e v ie w u n der tak e n t o i de n tif y ac tu a l or
po t en t ia l h a za rds t o h um an h ea l th in a wa te r
tr e atm e nt work s a nd a s s oc ia te d s u p pl y s ys t e m .
Pr i ori t is at i on of r is k is b as ed o n c o ns id er at i o n of
l ik el i ho o d a nd c ons e q ue nc e o f t h e r is k oc c u rri ng .
S ec r et ar y of St at e
S ec re t ar y of St at e f or E n vi ro nm en t, Fo o d
an d R ur al Af f airs .
S el en ium
is a n es s en t ia l e l em en t an d a n ec es s a r y d ie t ar y
c om pon e nt . Am ou n ts i n dr ink i n g wa t er ar e
us u a l l y we l l b e l o w t he s ta n dar d. A E ur op e an
he a lt h- b as e d s t an d ard of 1 0 μ g/ l a pp l i es .
S erv ic e co nne ct ion
c on n ec t i on be t we en t h e wa t er c om pa n y's m a i n
to a c ons um er’s p ro p e rt y.
S erv ic e pip e
an y p i p e s u bj ec t to m ai ns wa ter pres s ur e or
s ubj ec t t o m ai ns pres s ure bu t f o r th e c l os in g
of s om e v a l v e.
S erv ic e r e se rv oi r
a wa t er to we r, t ank or ot h er r es er vo ir us e d
f or t h e s tor a ge of tr ea t ed wa ter wi th i n t he
d is tr i bu t io n s ys t em .
Sug ge st ed n o adv e rs e
re sp on se l ev e l ( S N ARL)
a l e ve l of s u bs t a nc e a t wh ic h n o a d v ers e ef f ec ts
wo u ld be a n tic i p at e d.
Sod iu m
is a c om po n en t of c om m on s a l t. I t is pr es en t
i n s ea wa t er a nd brac k i s h gr ou n d wat er .
S om e tr ea tm en t c hem i c a ls c on t ai n s o d ium .
Co nc en tr at i ons in d ri n k ing wat er ar e ex tr em e l y
l o w, bu t s om e wa ter s of te n ers c a n a dd
s i gn if ic a nt am o un ts to dr ink i n g wa ter wh er e t he y
ar e ins t a ll e d i n h om es or f ac t or i es . A na t io n a l
s ta n dar d of 2 00m g/ l a pp l i es .
102
Western region
Sp ri ng s
wh er e wa t er na t ura l l y em erg es f rom b e lo w
gro u n d.
Su lph at e
oc c urs na tu ra l l y i n a l l wa ters an d is dif f ic u lt to
rem ov e b y tr e atm en t. A n i nd ic at or p ar am ete r wit h
a g ui d e v a lu e of 2 50m g/ l .
Sup pl y pip e
s ee s er vic e p i p e.
Sup pl y poi nt
a p oi n t ot h er th a n a c o ns um er ’s ta p a ut h or is ed
f or t h e tak i ng of s am p l es f or c om pl ia nc e wi t h
th e R eg u la t io ns .
Su rf ac e w at e r
un tr ea te d wat er f rom ri v ers , im p ou n di n g
res e r vo irs or ot he r s ur f ac e wa t er s o urc e .
T aste
c an aris e as a c ons e q ue nc e of na tu ra l pr oc e s s es
i n s urf ac e wa t ers , p ar t ic ul ar l y b et we e n l at e
s pr in g a n d ear l y a u tu m n. W ater tr e atm en t w it h
ac t i v at e d c ar bo n or o z on e wi l l r em ov e n at ur a l
s ubs t anc es c a us in g t a s te . T h e s ta n da rd r el a tes
to t h e e va l u at i ons of a p a ne l of p eo p le as s es s i ng
s am pl es i n th e l a bo ra t or y.
T echn ic al aud it
th e m ea ns of c h ec k in g t ha t wa t er c om pa n ies are
c om pl yi n g wi th t h ei r s t at ut or y o b l ig a ti o ns .
T etra ch lo ro et h an e an d
T rich lo ro et h en e
are s ol v e nts t h at m a y oc c ur in gro u nd wa t er i n
th e v ic i n it y of i nd us tr i a l s it es . W here n ec es s ar y
th e y ar e r em o ve d b y s pec i a l is t tr e atm en t.
A E ur op e a n he a lt h - b a s ed s t a nd ar d of 10 μg / l
f or t h e s um of b o th s u bs t a nc es a p p li es .
T etra ch lo ro met han e
is a s o l v en t t ha t m a y o c c ur i n gr ou n d wat er in t he
v ic in i t y of in d us tr i a l s i t es . W here n ec es s ar y i t is
rem ov e d b y s p ec i a l is t wa ter t re atm e nt.
A n at i on a l s t an d ar d of 3 μg / l ap p l ies .
T ime of sup pl y
th e m om ent wh en wa t er p as s es f rom th e wa ter
c om pan y’ s pi p e work i n to a c ons um er’s p i p e work .
T otal ind ic at iv e d o se
is a m eas ur e of th e ef f ec t i v e d os e of r a d ia t io n
th e b od y wi l l rec e i ve f rom c ons um pt i on of t h e
wa ter . It is c a lc u l at e d on l y wh e n s c r ee n in g
v a lu es f or gr os s a lp h a or g ros s b e ta (r ad i at i on)
are ex c e e de d . A n i nd i c at or p ar am eter wi th a
gu i d e v a lu e of 0. 1 0m Sv/ ye a r.
T otal o rg an i c c a rb on
rep res e nts t he t o ta l a m ount of or g an ic m att er
pres e nt in wa ter . A n i n d ic a tor par am et er wi t h
a g ui d e v a lu e of ‘ n o a bn orm al c ha n ge ’ .
T oxic olo g y
th e s t ud y of t he h e a lt h ef f ec ts of s u bs t a nc es .
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Drinking water 2015
T reat ed w at e r
wa ter t re at e d f or us e f or d om es tic pur p os es as
def in e d i n th e R eg u l at i ons .
T riha lo met ha ne s
ar e f orm ed d ur i ng d is i nf ec t i o n of wat er b y a
r eac t io n b e t wee n c h l or i ne a n d n at ur al l y oc c u rri ng
or g a n ic s u bs t anc es . T he ir p ro d uc t i on is
m inim is e d b y g o o d op er a t io n a l pr ac t ic e.
A E ur op e a n he a lt h - b a s ed s t a nd ar d of 10 0 μ g /l
ap p l ies .
T ritiu m
is a ra d i oac t i ve is o to p e of h ydr o ge n .
Dis c h ar ges t o t he e n v i ronm e nt ar e s tr ic t l y
c on tr ol l e d a nd t h ere is a n a ti o na l p ro gr am m e
of m on it or in g s urf ac e wa ters . A n i n d ic a to r
par am et er wi t h a g u id e v a lu e of 1 00 B q/ l .
T urbid it y
is a m ea s ur e of th e c l ou d i nes s of wa t er. At
tr e atm e nt work s , m eas urem e nt is an im port a nt
no n- s p ec if ic wa t er q ua l it y c o n tro l p ar am eter
bec a us e it c a n b e m o n it or ed c on t in u ous l y o n - l in e
an d a l arm s s et t o a l ert o p era to rs to d e ter i or a ti o n
i n r a w wat er q u a li t y or t he ne e d to o p tim is e
wa ter t re atm e nt. A n i n d ic a tor par am et er wi t h a
gu i d e v a lu e of 1NT U . W hen d et ec te d a t th e
c ons um er’s t a p i t c an ar is e f rom d is t ur ba nc e of
s ed im en t wi t h in wa ter m ains . A n at i on a l s t an dar d
of 4 NT U ap p l i es i n th i s c as e.
Ult r av iol et t re at m ent
th e us e of ul tr a v io l et li gh t t o k i l l pa t ho g en ic
m ic roor g an is m s , f or e x am pl e Cry p t os p or i di u m .
Und er ta ki ng s
Le g a ll y- b i nd i n g pr ogr a m m es of work ag re e d
be t we en a wa te r c om pan y a n d t he C h ief
Ins p ec t or of D ri nk i ng W ater t o ad dr es s ac tu a l or
po t en t ia l wat er q u al i t y is s u es , f or c om pl e ti o n
wi t hi n a s p ec if i e d tim e p er io d .
Vi n yl ch lo rid e
m a y be p res e nt i n p l as tic pi p es as a res i d ua l of
th e m an uf ac tu ri n g pr o c es s of po l yv i n yl c hl or i de
( P VC ) wa ter p ip es . I ts pr es enc e i n dr i nk in g wa ter
is c o ntr o l le d b y pr o d u c t s pec if ic a t io n.
A E ur op e a n he a lt h - b a s ed s t a nd ar d of 0. 5 μ g/ l
ap p l ies .
W ate r s upp l y z on e
a pr e- d ef i n ed are a of s up p l y f or es t a b lis h i ng
s am pl i ng f re qu e nc ies , c om pl i anc e wi t h s t an d ards
an d i nf orm at i on t o b e m ade p ub l ic l y a v a il a b l e.
W HO
W orld H e a lt h O r g an is a ti o n .
W hol es om e/w hol e so men e ss
a l eg a l c o nc e p t of wat er q ua l it y wh ic h is d ef i ne d
b y r ef er e nc e t o s t an d a rds a nd o t her
r eq u ir em ents s et o ut i n th e R eg u l at i ons .
104
Drinking water 2012
Drinking water
2012
Public water supplies in the
Western region of England
July 2013
A report by the Chief Inspector of Drinking Water
Public water supplies in the Western region of England
Drinking Water Inspectorate | Nobel House, 17 Smith Square | London | SW1P 3JR | Tel: 0300 068 6400
www.dwi.gov.uk