2010 Water pressure
management trial
Waterford, Shelley and Rossmoyne
Table of Contents
Executive Summary
Background
Method
Project Objectives and Conceptual Approach
Selection of Trial Areas
Water Corporation Commitment
Stakeholder Management
Project Issues
Data Capture and Analysis
Technical and Maintenance Issues
Results
Waterford Water Savings and Costs
Shelley Water Savings and Costs
Rossmoyne Water Savings and Costs
Customer Impacts
Conclusions
Recommendations
Waterford, Shelley and Rossmoyne Trial Areas
Expansion to Other Areas
Where to from Here
3
5
6
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10
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14
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Appendix
Appendix
Appendix
Appendix
Appendix
Appendix
Appendix
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30
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A – Consumption Analysis
B – Background Leakage Analysis
C – Leaks and Bursts Incidents
D – Exit Survey Analysis
E – Flow Modulation PRV Settings
F – Capital and Operating Expenditure
G – Derivation of Possible Future Costs and Benefits
Date
10 July 2009
27 July 2009
6 August 2009
20 August 2009
12 February 2010
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Description
Final Report
Final Report
Final Report
Final Report
Final Report
Rev
Rev
Rev
Rev
2010 Water pressure management trial
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Author
Rod Burton
Rod Burton
Rod Burton
Rod Burton
Rod Burton
Executive Summary
Water supply pressure reduction is a measure which has the potential to reduce consumption
and water loss due to leakage. Reduction of leaks and bursts incidents and extension of asset
life are likely additional benefits.
In late 2006, the Corporation commenced a trial project to reduce water pressure in the
suburbs of Waterford, Shelley and Rossmoyne which had been identified as high pressure (>60
metres), and high consumption or high reported leaks and bursts areas. Pressure management
areas involving 650 services in Waterford, 927 in Shelley and 1499 in Rossmoyne were defined
and a communications program with affected customers was initiated.
In March 2007 a pressure reducing valve (PRV) on the main supplying Waterford was
commissioned. The PRV is equipped with a flow controller programmed to ensure the
designated reduced pressure is maintained at the critical pressure point over a wide range of
demand flows. Flow controlled PRVs were installed on mains supplying major parts of Shelley
and Rossmoyne and pressure reduction commenced in these areas in January 2008.
A reduction of pressure to a minimum of 35 metres had previously been identified as an
optimum pressure to satisfactorily operate well designed reticulation systems. Internal house
plumbing would be satisfactory at a pressure of 25 metres. In all three pressure management
areas pressure was reduced from about 60 metres to a minimum of 35 metres.
After some months of adjustment and understanding operations and maintenance issues, the
outcome for the 12 months from May 2008 to May 2009 is as follows:
•
reductions in residential water consumption resulted in total water supplied reducing by
10.9%, 7.0% and 8.3% for Waterford, Shelley and Rossmoyne respectively;
•
estimated water savings due to reductions in background leakage and leaks and bursts
incidents of 2.1%, 4.0% and 8.7% of total water supplied to Waterford, Shelley and
Rossmoyne respectively;
•
•
substantially reduced levels of leaks and bursts incidents in Shelley and Rossmoyne;
•
positive financial outcomes for all three pressure management areas in terms of the value
of water saved compared with the cost of achieving the saving.
a low level of customer complaints matched by a demonstrated level of customer
satisfaction;
Based on these outcomes, from both sustainability and financial perspectives, it is
clearly evident that pressure management can be implemented with economic
benefits and with minimal impact on customers.
For Perth, with significant water source capacity augmentation expenditure for the foreseeable
future, and with calculated real water losses of 19 GL per year in 2007/08, expansion of
pressure management to a significant program appears justified.
The process of moving forward to implementing a more widespread pressure management
program would involve undertaking a strategic study to determine the extent of coverage, the
rate at which the program should be implemented, and to prioritise areas for inclusion. The
study would also identify human and financial resources as well as accountabilities for
implementation of the program, and could be completed by December 2009. In the longer
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2010 Water pressure management trial
term the study should be expanded to include regional schemes where investment to meet
growing demand is planned or the cost of supply to existing communities is high.
Indicatively though, a target to achieve 30% of the Perth metropolitan area with pressure
managed down from 50 – 60 metres to a minimum of 35 metres over a period of 10 years
would require:
•
dedicated human resources with appropriate training for planning, design, project
management, operation and maintenance – in the order of 10 FTEs;
•
•
a capital budget in the order of $3.5 million per year;
an operating budget for ongoing maintenance increasing from $0.32 million in year one to
$3.2 million in year ten.
Based on outcomes from the trials in Waterford, Shelley and Rossmoyne, potential total water
savings of an estimated 11.25 GL per year could be expected by year ten. This would be made
up of:
•
•
5 GL per year from reduced customer demand;
6.25 GL per year from reduced water loss due to background leakage and reported leaks
and bursts.
Water Forever planning predicts the gap between supply and demand for water sources
supplying Perth to increase by over 6 GL per year for the foreseeable future. Additional new
water sources will be required to close this gap. Water saving through pressure management
provides the opportunity to defer capital investment in new source development.
Over a period of 50 years, the pressure management program proposed would require an
estimated present value expenditure of $79 million, producing water at an average cost of
$0.49 cents per kilolitre. Using the Long Run Marginal Cost financial model, the deferral by 2
years (in 10 years time) of all future new sources of water for the next 50 years produces a
present value saving between $180 million and $200 million depending on climate scenarios.
This saving comes from the deferral of both construction and operating costs.
These economic benefits of pressure management do not include consideration of extension of
asset life of the water distribution network, nor any analysis of enhanced Corporate reputation
or lower greenhouse gas emissions based on reduced water loss.
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2010 Water pressure management trial
Background
In late 2006 a commitment was made by
the Water Corporation to gain an
understanding of the potential for saving
water by reducing excessive pressure in
Perth’s water distribution network – thus
contributing to the aims of a water
sensitive city. Trials were initiated in 3
Perth suburbs to investigate consumption
and leakage reductions directly attributable
to reducing system pressure, and
additionally, to evaluate costs, technical
issues and customer impacts.
Drivers for improved water efficiency
across all sectors have been population growth and the drying climate in the South West of
Western Australia combining to put unprecedented stress on the capacity of water sources to
meet demand. The cost of developing new water sources has increased disproportionately
leading to reconsideration of water saving initiatives once considered unviable.
In summary, Perth’s water supply scheme consists of 10 surface water and 8 ground water
sources, and a recently completed seawater desalination plant, connected via treatment plants
and pumping stations through trunk mains to a number of service reservoirs. A network of
distribution/reticulation pipes supplies customers either from the service reservoirs, or directly
from the trunk mains.
Within the Water Corporation’s Operating Licence water pressure to customers is allowable in
the range from 15 metres to 100 metres. It has been estimated that water pressure to about
50% of Perth customers exceeds 50 metres and there are a number of isolated hills areas
where pressures of up to 100 metres exist. This situation presents an opportunity for
reductions in excessive pressure and the associated potential for water saving.
Although a 17% reduction has been achieved since 2001, water consumption in Perth remains
relatively high at around 150 kilolitres per person per year. In 2007/08 residential
consumption was 72% of the total, non-residential consumption accounted for 20% and the
remaining 8% was non-revenue water made up of operating consumption, fire fighting usage
and water loss.
Approximately 50% of residential consumption in Perth is used ex-house on lawns and gardens.
Large residential lot sizes, sandy soils and hot windy conditions over summer are major
contributors to the high ex-house consumption.
The proliferation of automatic garden watering systems, many inefficiently designed and poorly
maintained, together with lingering “set and forget” behaviour and relatively inexpensive
consumption charges, combine to deliver the potential for water wastage. Water loss in the
Perth scheme, as measured by the nationally and internationally reported Infrastructure
Leakage Index, is similar to other Australian capital cities, low by world standards, but high
enough to suggest that opportunities for improvement exist. With predominantly stable ground
conditions and relatively young infrastructure, a widespread active leak detection program
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2010 Water pressure management trial
would be inappropriate over much of the scheme. Use of sound asset management planning
though could identify specific opportunities in both pressure management and active leak
detection and repair.
One lesson learnt from recent implementation of many water efficiency initiatives by the Water
Corporation is that customers need help in finding ways to save water. Excessively high water
pressure is recognised as unhelpful for customers, as well as for scheme management, in
achieving water savings.
Method
Project Objectives and Conceptual Approach
The primary objective of the trials was to determine, in economic and customer impact terms,
the viability of pressure management as a means of achieving water savings. To achieve this,
the conceptual approach was determined to be:
•
•
•
•
•
•
communication with affected customers;
incremental elimination of excessive pressure;
measurement of consumption reduction;
measurement/calculation of reduced water loss through leakage;
understanding the impact of pressure reduction on leaks and bursts incidents; and
evaluation of costs and tracking of customer issues.
Selection of Trial Areas
The residential suburb of Waterford (650 water services) was identified as having potential for
water saving based on a combination of high scheme pressure (60 metres) and high customer
water consumption. With a relatively young and sound pipe network having few leaks and
bursts incidents, the focus for Waterford was primarily on the reduction in customer
consumption from reduced pressure. Flat terrain and the relative ease of isolating the pipe
network and achieving reduced pressure were also contributing factors in the selection of
Waterford.
Adjacent residential areas of Shelley (927 water services) and Rossmoyne (1499 water
services) were chosen based on the potential for reduction in leaks and bursts incidents, and
reduced water loss through suspected higher than average background leakage. High water
pressure (60 metres), relatively flat terrain, and comparatively simple pressure management
implementation were also factors in the selection of Shelley and Rossmoyne.
Because of the many seasonal and behavioural influences on water consumption, control areas
were selected in Salter Point for Waterford and in Riverton for Shelley and Rossmoyne. Salter
Point and Riverton are suburbs located nearby to Waterford and Shelley/Rossmoyne
respectively, and have similar demographics. The control groups allowed comparison of
consumption change under unchanged pressure conditions with consumption change under
reduced pressure in the trial areas.
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2010 Water pressure management trial
Figure 1 – Trial Areas for Pressure Management
The Waterford pipe network is predominantly cast iron and PVC approximately 20 years old,
while the Shelley and Rossmoyne pipes are mainly asbestos cement and cast iron about 50
years old.
Water Corporation Commitment
Although pressure management as a water saving measure was identified early in the current
drive for improved water efficiency, its implementation was delayed due principally to the lack
of knowledge regarding costs and benefits. Added to this though was the perception that likely
customer dissatisfaction would be in direct conflict with the strong customer service ethic
deeply ingrained in Water Corporation culture.
Other issues such as funding approvals, accountabilities across several parts of the
organisation, and the resourcing of planning, design, project management and implementation,
were hurdles to be overcome before even trials of pressure management could be commenced.
Eventually though in late 2006, with encouragement from the Perth news media, resourcing
commitments were made and the task of achieving trial areas of reduced pressure was fasttracked.
Stakeholder Management
A communications program was developed and implemented to keep affected customers
involved and informed before and during the project. The program consisted of letter drops,
information in local newspapers, and meetings with residents, the local authorities and
Members of Parliament. Near the conclusion of the trials a newsletter and questionnaire were
delivered to all affected customers, seeking information about the impact of pressure reduction
inside and outside the home.
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2010 Water pressure management trial
Independent testing of garden reticulation systems determined that effectively designed,
installed and maintained systems would operate satisfactorily at pressures of 30-35 metres.
Advice was received from the plumbing industry that household plumbing and all domestic hot
water systems would operate satisfactorily down to pressures of 25 metres.
A complaints handling procedure was established. All customer calls were relayed to the Call
Centre which initiated an inspection by Water Corporation officers to determine the underlying
cause and provide some advice. Customers with garden reticulation issues were given access
to a free audit of their irrigation system from their choice of nominated Waterwise accredited
reticulation businesses.
The possible impact of reduced pressure on fire fighting was recognised and the matter was
considered from the conceptual stages in regular meetings with the Fire and Emergency
Services Authority (FESA). Liaison with FESA has continued through commissioning of pressure
reducing equipment and testing to examine and confirm satisfactory response of the pressure
reducing equipment to provide adequate fire fighting flows.
Project Issues
While the Water Corporation has had considerable experience in the use of Pressure Reducing
Valves (PRVs) in water supply schemes throughout the State over many years, the inclusion of
flow modulation to control pressure to customers was new. In designing the equipment layout
and performance requirements, assistance was obtained from commercial suppliers of PRVs
and flow controllers. Consideration of Occupational Safety and Health issues directed that the
PRVs and flow controllers be installed in above ground cabinets.
Conceptually, the flow modulated PRVs respond to changing instantaneous metered demand so
that pressure is maintained at a predetermined value (minimum 35 metres) at the critical
pressure points in the area. In the design process, hydraulic modelling for accurate
determination of critical pressure points is therefore of significant importance.
Negotiations with local authorities in selection of a mutually satisfactory site for each of the
control equipment cabinets proved to be time consuming and contributed to delays in
implementing the trials. Configuration of the pipe network supplying each pressure
management area has a controlling influence limiting options available for locating the PRV.
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2010 Water pressure management trial
Figure 2 – Waterford Cabinet
Figure 3 – Waterford PRV and Flow Controller
Positioning of the control cabinets was largely governed by configuration of the pipe network
which feeds the pressure management areas. In built up areas this created difficult site
selection issues for resolution with local authorities and affected land owners and custodians.
The main criteria was to make the installations as visually unobtrusive as possible but the
cabinets becoming graffiti targets has been an issue directly conflicting with this objective.
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2010 Water pressure management trial
Data Capture and Analysis
Yearly water consumption information for the trial areas and the control groups was obtained
for the six years prior to pressure reduction. The average annual consumption over those six
years was compared with annual consumption after pressure reduction, and the differences
adjusted by reference to the control groups.
Continued media interest hastened the reduction in pressure, and monthly minimum night
flows before pressure reduction commenced were not obtained except for a period of 4 months
for Waterford. Determination of the reduction in background leakage due to pressure reduction
has therefore been based on theoretical calculations using as a basis minimum night flows
recorded after pressure reduction had been implemented.
Observed reductions in minimum night flows for Waterford, by comparing the few months of
pre and post pressure reduction information, provide some support to the theoretical
calculations.
Technical and Maintenance Issues
In all three trial pressure management areas it has been necessary to make adjustments to the
flow controlled downstream pressure of the PRVs to cover the wide range of seasonal peak
flows being experienced. This activity has been intensified by the need to redefine locations of
the critical pressure points.
PRV failure has occurred on several occasions due to excessive build up of deposits in small
orifices of the control pipework. Although some improvements have been made in the form of
filters and the use of stainless steel, this is an ongoing issue for which frequent preventive
maintenance appears to be the only workable solution.
Availability of staff skilled in maintenance of the flow modulated PRVs is an issue to be
addressed if pressure management is to be implemented on a wider scale.
Pressure reduction has highlighted weaknesses in the distribution pipe network by identifying
pipes carrying high flows and therefore excessive pressure losses. In these cases even more
effective pressure management would be possible with relatively simple improvements to the
distribution system.
Isolation of each pressure management area to a single supply main through the PRV
highlighted the need for well maintained system valves and accurate “as constructed”
information of the pipe network.
PRV maintenance has meant that on several occasions it has been necessary to bypass the PRV
and return the area to its original pressure. Although an increase in leaks and bursts incidents
could have been anticipated in this scenario, no immediate identifiable impact was experienced.
Nevertheless, in any future roll-out of pressure management, consideration should be given to
provision of a back-up PRV, or temporary supply from an adjacent pressure managed area, to
provide for shut down of the duty PRV.
Selection of PRV size is critical to the success of flow modulation. An oversized PRV can lead to
failure of the flow control system during extremely low flows. For areas where minimum night
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2010 Water pressure management trial
flows are very low, automatic bypassing of the main PRV to a smaller PRV is currently being
investigated.
Results
Results for the trial pressure management trials are based on measured consumption, flow
records, leaks and bursts incident data, customer issues and costs up to May/June 2009.
Waterford Water Savings and Costs
Category
Consumption
Background leakage
Leaks and bursts
Number of phone
contacts and home
visits
$costs/$savings
Outcome
Reduced by 50.5 kL per service per year giving an estimated
32840 kL per year saving (10.9% saving on total water
supplied)
Estimated reduction of 6220 kL per year (2.1% saving on total
water supplied)
No change – average 1 per year
2.9 per 100 services per year – majority have been garden
irrigation related leading to a total of 6 free irrigation system
audits
Costs:
Annualised capex (20 year life, 6% interest)
$12,430
Operations & maintenance per year
$16,480
Revenue loss per year@ $1.00 per kL*
$32,840
Total cost per year
$61,750
Savings:
Consumption & leakage @ $1.70 per kL**
$66,400
Reduction in leaks & bursts incidents per year
$0
Total savings per year
$66,400
Unit cost of water saved:
$0.74 per kL
* Note:
$1.00 per kL is the approximate average price of water, based on advice from
Pricing and Evaluation Branch.
** Note:
$1.70 per kL is based on advice from Pricing and Evaluation Branch regarding the
future cost of additional water source development. Production cost of water is approximately
$0.30 per kL for groundwater and $1.00 per kL for desalination.
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Shelley Water Savings and Costs
Category
Consumption
Background leakage
Leaks and bursts
Number of phone
contacts and home
visits
$costs/$savings
Outcome
Reduced by 24.6 kL per service per year giving an estimated
22790 kL per year saving (7.0% saving on total water supplied)
Estimated reduction 8940 kL per year (2.8% saving on total
water supplied)
Reduced from 5 per year to 3 per year for estimated saving of
4000 kL per year (1.2% saving on total water supplied)
3.4 per 100 services per year – majority have been garden
irrigation related leading to a total of 4 free irrigation system
audits
Costs:
Annualised capex (20 year life, 6% interest)
$12,990
Operations & maintenance per year
$11,800
Revenue loss per year @ $1.00 per kL
$22,790
Total cost per year
$47,580
Savings:
Consumption & leakage @ $1.70 per kL
$59,980
Reduction in leaks & bursts incidents per year
$4,000
Total savings per year
$63,980
Unit cost of water saved:
$0.58 per kL
Rossmoyne Water Savings and Costs
Category
Consumption
Background leakage
Leaks and bursts
Number of phone
contacts and home
visits
$costs/$savings
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Outcome
Reduced by 38.7 kL per service per year giving an estimated
57970 kL per year saving (8.3% saving on total water supplied)
Estimated reduction 50730 kL per year (7.5% saving on total
water supplied)
Reduced from 8 per year to 3 per year for estimated saving of
10000 kL per year (1.4% saving on total water supplied)
1.0 per 100 services per year – majority have been garden
irrigation related leading to a total of 2 free irrigation system
audits
Costs:
Annualised capex (20 year life, 6% interest)
$12,990
Operations & maintenance per year
$11,800
Revenue loss per year @ $1.00 per kL
$57,970
Total cost per year
$82,760
Savings:
Consumption & leakage @ $1.70 per kL
$201,790
Reduction in leaks & bursts incidents per year
$10,000
Total savings per year
$211,790
Unit cost of water saved:
$0.12 per kL
2010 Water pressure management trial
Customer Impacts
A further matter for consideration is one of equitable treatment of customers adversely
impacted by a lower water pressure than they had previously experienced. Although the
intention of the trials was to only eliminate excessive pressure, it is apparent that for some
customers satisfactory operation of internal plumbing and/or garden irrigation systems relied
on pressures higher than the 35 metre minimum provided.
Anecdotal evidence from both plumbers and garden irrigation professionals indicated that in
some properties substandard workmanship existed which had been compensated for by the
original high water pressure provided. The incidence of substandard garden irrigation systems
was greater than that for internal plumbing.
Over the period of the trials a total of 80 enquiries and complaints were received from the 3076
services. These customer contacts focussed principally on garden irrigation systems and the
performance of internal household plumbing.
To gain a better understanding of the nature and extent of customer impact an exit survey of
the occupiers of all affected properties was conducted in May 2009 to coincide with the
completion of the trial period. A newsletter with a summary of the trials and preliminary
results, and a postage paid tear-off questionnaire, was hand delivered to every household.
7.1% of households completed and returned the questionnaire, and their responses covered a
broad range of impacts and attitudes from negative to positive.
In summary, the responses indicated
•
a high level of awareness of the trials principally due to the Corporation’s communication
program;
•
just under half (47%) of the respondents felt they were unaffected by the trials, while 8%
and 17% respectively experienced a major effect inside and outside their house;
•
22% of respondents have made changes to internal water using appliances and 29% have
made changes to the way water is used externally;
•
47% of respondents have experienced a negative impact from reduced water pressure
while 53% have not;
•
7% of respondents experienced an positive impact while 88% did not – 5% were
undecided;
•
68% of respondents believed that pressure management should be extended to other
areas, 24% did not and 8% were undecided.
A comprehensive analysis of the questionnaire responses with specific comments from
respondents is included at Appendix D.
Conclusions
Results of water savings and costs analysis indicate that sustainable outcomes have been
achieved from the pressure management trials in Perth. Water savings come from reduced
customer consumption, reduced background leakage and fewer numbers of leaks and bursts
incidents.
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2010 Water pressure management trial
Based on the analysis of data up to May/June 2009 pressure management trials, reducing
pressure from about 60 metres to a minimum of 35 metres, have produced the following
conclusions:
•
Water consumption savings resulted in total water supplied reducing by 10.9% for
Waterford, 7.0% for Shelley and 8.3% for Rossmoyne respectively.
•
Background leakage has reduced total water supplied by 2.1%, 2.8% and 7.5% for
Waterford, Shelley and Rossmoyne respectively, with the greatest saving in the area with
highest leaks and bursts incident rate.
•
Leaks and bursts incidents have reduced significantly especially in areas with higher leaks
and bursts incident rates – Shelley and Rossmoyne.
•
Customer contacts have been minimal at between 1% and 3% per year. The
comprehensive communication program implemented is believed to be primarily
responsible for achieving this level of community buy-in.
•
$ savings and $ costs are of similar magnitude for the high consumption/low leaks and
bursts area (Waterford) and the unit cost of water saved is significantly lower than the
estimated long run marginal cost of new water for all areas.
•
$ savings compared to $ costs are very favourable for high leaks and bursts areas (Shelley
and Rossmoyne), and would be further improved by extension of asset life considerations,
and greenhouse gas emissions reductions, which have not been included in the analysis.
•
Improved valve operation and maintenance, and distribution pipe network management,
are integral aspects to the implementation of pressure management. It has been observed
that relatively small improvements to distribution system network could improve the
effectiveness of pressure management where small diameter pipes supplying the critical
pressure points are carrying high flows and therefore incurring excessive pressure losses.
•
Testing by FESA has resulted in satisfactory response times of the PRVs in providing
required fire fighting flows.
•
Elimination of excessive pressure in other high consumption areas and/or high leaks and
bursts incidents areas of Perth appears to be justified based on results obtained to date
from the trial pressure management areas in Waterford, Shelley and Rossmoyne.
Recommendations
Waterford, Shelley and Rossmoyne Trial Areas
The success of the trial pressure management areas in Waterford, Shelley and Rossmoyne in
terms of effective economic outcomes and minimal adverse customer impact, points to the
obvious conclusion that these areas should be retained for the foreseeable future. However,
compared to total Perth consumption, water saved in the trial areas is a minute 0.1% and
therefore continuation without wider expansion may be difficult to justify due to perceived
equity issues.
It is recommended therefore that the trial areas be continued indefinitely subject to the
Corporation’s ongoing intention, and demonstrated confirmation, to expand pressure
management on a permanent basis to other parts of the metropolitan area.
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2010 Water pressure management trial
Expansion to Other Areas
In the first instance, expansion to other parts of the Perth metropolitan area requires a
strategic study to identify those regions where implementation of pressure management is
justified. Specifically these areas would have static pressures exceeding 50 metres and either
high levels of reported leaks and bursts or high residential water consumption, or both.
The strategic study would also give consideration to, and make recommendations regarding,
resources and timing for implementation of an expanded pressure management program. It is
envisaged that use would be made of engineering consultants for this study.
It is recommended therefore that expressions of interest be obtained as soon as possible from
suitable engineering consultants to conduct a planning project in conjunction with Strategic
Asset Management Branch. Involvement from Infrastructure Planning Branch, Tactical Asset
Management Branch and Operational Asset Management Branch in the strategic study would be
essential.
Where to from Here
A preliminary appraisal of consumption patterns and the spatial density of reported leaks and
bursts indicates that for approximately 30% of the metropolitan area a pressure management
program would be justified.
Based on the trial areas, expansion of pressure management to 30% of the metropolitan area
would require capital expenditure of $35 million over say 10 years and an additional operating
budget increasing from $320,000 to $3.2 million per year over the same period. It would
involve some 150 – 200 pressure management areas in total and be expected to save 11.25 GL
of water per year. Implementation would require an estimated 10 FTEs for planning, design,
project management and ongoing operation.
Saving water through pressure management supports one of the key directions in the
Corporation’s Water Forever plan. The pressure management trials have indicated that
expansion to other selected parts of the metropolitan is justified. The Corporation’s capital and
operating budgetary processes should therefore be used to allocate funding to a pressure
management program as soon as practicable.
It is recommended that capital funding of $3.5 million per year be set aside for a period of 10
years, and operational funding of $320 000 per year be allocated in year one increasing to $3.2
million per year in year ten. It should be recognised that these funding amounts are
preliminary estimates and may need to be modified based on the findings of the strategic
study.
Initially though, the strategic study mentioned above should be commissioned and scheduled
for completion by December 2009. Funds are available for this study in the 2009/10 New
Initiative project for water loss management.
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2010 Water pressure management trial
Appendix A – Consumption Analysis
Waterford pressure management area:
Average consumption 01/02-06/07
Average consumption 08/09
Consumption reduction
=
=
=
425.37 kL/service/year
381.70 kL/service/year
43.67 kL/service/year (10.27%)
=
=
=
334.62 kL/service/year
340.01 kL/service/year
5.39 kL/service/year (1.61%)
Salter Point control area:
Average consumption 01/02-06/07
Average consumption 08/09
Consumption increase
Waterford PMA consumption reduction based on comparison with Salter Point control
area:
Consumption reduction % = 10.27 + 1.61 = 11.88%
Reduced consumption = 11.88 x 425.37/100 = 50.53 kL/service/yr = 32840 kL/year
Shelley pressure management area:
Average consumption 01/02-06/07
Average consumption 08/09
Consumption reduction
=
=
=
309.01 kL/service/year
281.24 kL/service/year
27.77 kL/service/year (8.99%)
=
=
=
336.86 kL/service/year
294.72 kL/service/year
42.14 kL/service/year (12.51%)
=
=
=
251.51 kL/service/year
248.92 kL/service/year
2.59 kL/service/year (1.03%)
Rossmoyne pressure management area:
Average consumption 01/02-06/07
Average consumption 08/09
Consumption reduction
Riverton control area:
Average consumption 01/02-06/07
Average consumption 08/09
Consumption reduction
Shelley PMA consumption reduction based on comparison with Riverton control area:
Consumption reduction % = 8.99 – 1.03 =
Reduced consumption = 7.96 x 309.01/100
7.96%
= 24.60 kL/service/year = 22790 kL/year
Rossmoyne PMA consumption reduction based on comparison with Riverton control
area:
Consumption reduction % = 12.51 – 1.03 = 11.48%
Reduced consumption = 11.48 x 336.86/100 = 38.67 kL/service/year = 57970 kL/year
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2010 Water pressure management trial
Appendix B – Background Leakage Analysis
Assumptions:
•
•
Minimum night flow is a combination of background leakage and water use.
•
Average recorded PRV pressure for 10 minimum night flows recorded in June/July 2009
used to determine background leakage under reduced pressure.
•
•
•
•
Based on interstate studies, 6% of people flush the toilet during min hour of the night.
Allowance made for small variations in recorded flows, and variable usage patterns, by
using average of lowest 10 minimum night flows recorded in June/July 2009.
Average toilet flush is 5 litres and occupancy rate of dwellings equals 3 per service.
Average pressure before pressure reduction equals 90% of maximum pressure.
Based on international studies, leakage is directly proportional to pressure raised to the
power of 1.15, but a more conservative estimate of water saved using a direct 1:1
relationship has been assumed.
Waterford
Average of lowest 10 minimum night flows recorded in June/July 2009 = 40.38 L/min
Average PRV pressure for same events
= 38.95 metres
Original pressure
= 60 metres
Number of services
= 650
Minimum night usage allowance = 650 x 3 x 0.06 x 5 / 60
= 9.75 L/min
Background leakage at reduced pressure = 0.673 x 60 – 9.75
= 30.63 L/min
Estimate of background leakage pre pressure reduction:
30.63 x (0.9 x 60) / 38.95
= 42.46 L/min
Estimate of water saved = (42.46 – 30.63) x 60 x 24 x 365/1000
= 6221 kL/yr
Shelley
Average of lowest 10 minimum night flows recorded in June/July 2009 = 52.74 L/min
Average PRV pressure for same events
= 37.55 metres
Original pressure
= 60 metres
Number of services
= 927
Minimum night usage allowance = 927 x 3 x 0.06 x 5 / 60
= 13.91 L/min
Background leakage at reduced pressure = 0.879 x 60 – 13.91
= 38.83 L/min
Estimate of background leakage pre pressure reduction:
38.83 x (0.9 x 60) / 37.55
= 55.84 L/min
Estimate of water saved = (55.84 – 38.83) x 60 x 24 x 365/1000
= 8942 kL/yr
Rossmoyne
Average of lowest 10 minimum night flows recorded in June/July 2009 = 259.20 L/min
Average PRV pressure for same events
= 38.36 metres
Original pressure
= 60 metres
Number of services
= 1499
Minimum night usage allowance = 1499 x 3 x 0.06 x 5 / 60
= 22.49 L/min
Background leakage at reduced pressure = 4.32 x 60 – 22.49
= 236.71 L/min
Estimate of background leakage pre pressure reduction:
236.71 x (0.9 x 60) / 38.36
= 333.22 L/min
Estimate of water saved = (333.22 – 236.71) x 60 x 24 x 365/1000 = 50726 kL/yr
17
2010 Water pressure management trial
Appendix C – Leaks and Bursts Incidents
2001/02
2002/03
2003/04
2004/05
2005/06
2006/07
Average
Number of Leaks and Bursts before Pressure
Management
Waterford
Shelley
Rossmoyne
0
6
7
1
4
6
2
3
6
1
3
6
0
10
8
0
2
13
0.7
4.7
7.7
2008/09
Number of Leaks and Bursts after Pressure Management
*
Waterford
Shelley
Rossmoyne
1
3
3
* NOTE:
18
Although not able to be confirmed, it is considered highly likely that some of the
leaks and bursts incidents recorded in 2008/09 were caused when pressure was
returned to original pressure due to PRV corrective maintenance events.
2010 Water pressure management trial
Appendix D – Exit Survey Analysis
Waterford Pressure Management Area
Response: 40 replies from 650 customers (6.2%)
Were you aware of the water network optimisation trials in your suburb?
Yes – 35 (88%)
No – 4 (10%)
Blank – 1 (2%)
If yes, was this from information you received from the Water Corporation?
Yes – 29 (83%)
No – 6 (17%)
Have you been affected by the network optimisation trials?
a) Inside your home:
Nil – 23 (58%)
Minor – 7 (17%)
Moderate – 6 (15%) Major – 4 (10%)
b) Outside your home: Nil – 20 (50%)
Minor – 8 (20%)
Moderate – 4 (10%) Major – 8 (20%)
Have you had to make any changes to your water-using appliances as a result?
a) Inside your home:
Yes – 11 (28%)
No – 29 (73%)
b) Outside your home: Yes – 14 (35%)
No – 24 (60%)
Blank – 2 (5%)
Have you experienced any negative impacts which you believe are the result of
reduced water pressure?
Yes – 20 (50%)
No – 20 (50%)
If yes, please summarise these:
Garden retic – 12
Reduced pressure in taps/shower - 12
Washing machine (time to fill) – 1
Upstairs cistern – 1
High pressure cleaner not working properly – 1
Gas storage HWS slow to fill and ‘popping’ – 1
Have you experienced any positive impacts which you believe are the result of
reduced water pressure?
Yes – 4 (10%)
No – 31 (78%)
Unsure – 5 (13%)
If yes, please summarise these:
Water use reduction – 3
Less water hammer – 1
Recommend expansion of Network Optimisation to other areas?
Yes – 28 (70%)
No- 10 (25%)
Blank – 2 (5%)
Comments:
1. Water retic now has coverage gaps. Have to lay new retic and piping. Will the Water
Corp cover the cost of this relaying?
2. First trial was fine. Second trial reduced water pressure dramatically.
3. Why don’t you fix the leaks?
4. Reduced water pressure did not pose any problem. Easily coped with the change.
5. We need to save water wherever we can. I haven’t noticed any change.
19
2010 Water pressure management trial
6. Waterford pressure, high before, has been reduced too much, needs adjustment back
up a little.
7. Slight conflict re which appliance takes preference. Can only have one household
appliance at a time eg w/machine or dishwasher or 3 min shower!
8. Very pleased we have a positive response.
9. Garden retic completely redone. Washing Machine and dishwasher slow to fill –
increased electricity costs. Additional wait time between showers, waiting for tank to
fill.
10. Less severe water hammer.
11. I’ve received widespread complaints from Waterford residents due to flow being
compromised.
12. Water pressure has never reached the promised 700kPa. Pressure has dropped to
150kPa hence no fire protection, FESA requires 250kPa minimum – dangerous,
negligent and incompetent.
13. This method is good for our state where water is an expensive resource.
14. Compensate households for low pressure sprinkler heads.
15. Not enough pressure to water garden beds in morning – changed to evening.
16. When retic is running, toilet will not flush and fill properly.
17. The decrease had no impact on our household – that indicates there may be a further
reduction to be tried.
18. No further reduction in Waterford.
19. Previously could have washing machine running and shower at same time with minimal
impact.
20. To cut back pressure is not successful as some areas now have to be hand watered.
21. We had no say at all in Waterford being a part of this trial although we pay rates and
water bills. Please increase water pressure so reticulation works properly.
22. Most of us are using more water by watering longer to compensate for low pressure.
Upstairs shower does not work when downstairs shower is in use. Yes all taps are on
full.
23. Was unable to install a Cleveland water saving device due to low pressure.
24. Pressure is too low.
25. Shower pressure no good and garden hose pressure no good.
26. Replaced toilets, shower roses, taps with high star rating appliances. Retic system
worked less effectively on low flow and dripper fittings. We lost plants. A neighbour
with all drippers lost most of the garden (natives) in both gardens. People face retro fit
costs on low flow retic. How about issuing a star rating for household water
consumption, on every water bill, (in addition to histogram comparison) similar to the
star rating on appliances and plumbing fittings? It may focus attention on the more
efficient fittings and encourage efforts to economise water use.
27. Pressure to the shower in ensuite is low. Pool filter isn’t as strong. Expand only of
public made fully aware.
28. The toilets smelt terrible - had to clean almost daily. Not sure if this due to lower
pressure but it has resolved now. Lower pressure in retic. If it reduced consumption
and loss by 10.5% that seems worthwhile. Still annoying to see public open space
being watered when it’s raining and household use is a small % of total water
consumption, so hope industrial use is being targeted too, not just ‘the little people’!
29. Using less water is good for our water resource in WA.
Shelley Suburb
20
2010 Water pressure management trial
Response: 81 replies from 1430 customers (5.7%)
Were you aware of the water network optimisation trials in your suburb?
Yes – 70 (86%)
No – 11 (14%)
If yes, was this from information you received from the Water Corporation?
Yes – 53 (75%)
No – 13 (19%)
N/A – 4 (6%)
Have you been affected by the network optimisation trials?
a) Inside your home:
Nil – 33 (41%)
Minor – 22 (27%)
Moderate – 17
(21%) Major – 9 (11%)
b) Outside your home: Nil – 31 (38%)
Minor – 19 (23%)
Moderate – 13
(16%) Major – 18 (22%)
Have you had to make any changes to your water-using appliances as a result?
a) Inside your home:
Yes – 16 (20%)
No – 65 (80%)
b) Outside your home: Yes – 26 (32%)
No – 55 (68%)
Have you experienced any negative impacts which you believe are the result of
reduced water pressure?
Yes – 42 (52%)
No – 39 (48%)
If yes, please summarise these:
Garden retic – 26
Reduced pressure in taps and/or shower – 14
Washing machine or dish washer (time to fill) – 8
Water Filter – 1
Toilet (time to fill) – 4
Toilet requires two flushes – 2
HWS drops out – 1
Have you experienced any positive impacts which you believe are the result of
reduced water pressure?
Yes – 1
No – 75 (93%)
Blank – 5 (6%)
If yes, please summarise these:
Hose fittings don’t blow off nowadays
Recommend expansion of Network Optimisation to other areas?
Yes – 51 (63%)
No- 25 (31%)
Unsure – 5 (6%)
Comments:
1. You should consider an increase to somewhere above 35m (maybe 45m) to give
reasonable pressure.
2. Roll out – definitely not. Water only dribbles out of taps (filter). Garden and plants die
– need replacing.
3. Our filter struggles to work. Shower, washing machine and retic affected. I have had
an increase in water usage which I believe is direct result of lower pressure. I have to
run the retic for extra time along with many other residents.
4. I have a bore and pump and use this for outside garden.
5. I expected problems with shower pressure and garden and lawn retic but both pressure
and flow is adequate in both situations.
6. Sounds like an effective solution to reducing water usage.
7. Neighbours have complained re-pressure on opposite side of street – not my side. Only
opposite??
21
2010 Water pressure management trial
8. Water pressure to backyard now poorer. Just put up with poor pressure. Suggest
Dalkeith/Mosman Park/Peppermint Grove council areas are next. This program, to be
equitable, needs to be introduced throughout metro area.
9. While it is annoying with sprinklers – happy to have seen general consumption gone
down.
10. You become acclimatised to new pressure. Great idea.
11. Our water has foul stench when boiled, occasionally. Also metallic taste, but not able to
pick the pattern (not chlorine either).
12. Spread the inconvenience. Pressure insufficient to rinse dishes, flush pool filters. Fix
the network, do not penalise users. Usage not reduced.
13. We should all be prepared to make some sacrifice for the good of all. Any savings in
water equates to savings in money, labour, taxes, natural resources etc.
14. We invite you to visit and see a demonstration of our reticulation system at work, and
the poor pressure inside the house.
15. If reduced pressure is going to help reduce burst pipes then I think it is a good thing.
16. If the strategy genuinely helps reduce water use and loss, it can only be good.
17. Our communal effort must always be to preserve resources, reduce waste, restore
ecosystems and to remain open-minded to ways in which these may be achieved.
18. Hasn’t been a noticeable difference at all. +ve impact is knowing it is a successful trial.
19. Hasn’t really affected us.
20. Great initiative and should be Australia wide.
21. Do not reduce any more.
22. Warn people and give them ideas – such as retic alternatives.
23. Don’t lower it too much in our area.
24. Have to flush toilet more than once to remove waste.
25. This is an unfortunate outcome. How can the WC return the pressure to normal?
26. The audit from Total Eden was a complete waste of time and money. This survey was
not delivered to my house.
27. I believe the pressure has been reduced too far. We have had sprinkler experts etc and
still our problem has not been resolved. This has been costly and inconvenient.
28. We are not in the position to renew retic. We feel we are using more water - hand
watering 2x a week in summer. Please go back to full pressure.
29. Fix the leaks. Only 3% less consumption. I have 4 kids an we can only use one
bathroom at a time.
30. Toilet cistern will not fill if sprinklers are on.
31. Dry patches in small garden.
32. Garden reticulation was greatly reduced, now need to run for longer period. My water
use has doubled in volume and cost due to running reticulation for longer time period
on regulation days.
33. Gas HWS (instant) drops out during showers. Were instant HWS’s considered with
implementing this trial?
34. Note that a significant % of the water saving was achieved through reduced water loss
(leakage?). reduced leakage loss through lower pressure surely just defers the
inevitable need to “fix the system”.
35. The reduced pressure needs to be increased.
36. We have noticed a major change in the pressure and are not happy about it. We have
had a consultant out to look at the retic but I don’t want to pay $1000’s, when in my
view it was working well before.
37. Two showers can not be used simultaneously, any use seriously reduces flow in other
parts of the property. Reticulation has had to be redesigned. Emergency use (eg Fire
fighting is seriously compromised).
38. Increase pressure a bit.
39. If this saves water I would support it.
40. Hose fittings don’t blow off the tap nowadays.
22
2010 Water pressure management trial
41. Showers and all taps need to be on full to get average water. Even tradesmen have
commented. I am concerned that the retic will be compromised as a result of the
reduced pressure in summer.
42. Shower pressure dropped, have to turn the tap on to get the pressure up for the hot
water to start.
Rossmoyne Suburb
Response: 98 replies from 996 customers (9.8%)
Were you aware of the water network optimisation trials in your suburb?
Yes – 92 (94%)
No – 6 (6%)
If yes, was this from information you received from the Water Corporation?
Yes – 79 (86%)
No – 9 (10%)
Blank or N/A – 4 (4%)
Have you been affected by the network optimisation trials?
a) Inside your home:
Nil – 47 (48%)
Minor – 26 (26%)
Moderate – 20 (20%)
Major – 5 (5%)
b) Outside your home: Nil – 52 (53%)
Minor – 16 (16%)
Moderate – 19
(19%) Major – 11 (11%)
Have you had to make any changes to your water-using appliances as a result?
a) Inside your home:
Yes – 21 (21%)
No – 77 (79%)
b) Outside your home: Yes – 24 (24%)
No – 66 (67%)
Blank – 8 (8%)
Have you experienced any negative impacts which you believe are the result of
reduced water pressure?
Yes – 42 (43%)
No – 56 (57%)
If yes, please summarise these:
Garden retic – 15
Reduced pressure in taps/shower – 22 (1 removed water efficient head)
Washing machine (time to fill) – 5
HWS – 6
Water quality - taste varies - 3
Water filter - 1
Have you experienced any positive impacts which you believe are the result of
reduced water pressure?
Yes – 11 (11%)
No – 87 (89%)
If yes, please summarise these:
Water use reduction – 5
Doing something helpful – 2
Appliances not failing – 2
Less hammer - 1
Recommend expansion of Network Optimisation to other areas?
Yes – 70 (71%)
No- 18 (18%)
Undecided – 10 (10%)
Comments:
1. Inconvenient! More watering time – no saving of water.
23
2010 Water pressure management trial
2. Longer to hand water plants and wash car – low pressure.
3. Modifications necessary to reticulation cost $300.
4. I don’t feel we use any less water as we need to run taps longer to reach the desired
effect and use. More frustration!
5. Why don’t you repair the leaks or renew the pipes – think of the future? Optimisationthis must mean cheapest repair option.
6. We pay for the water – so deliver it.
7. Fancy name. Biased research. Scare tactics on pressure demo. Stop wasting money on
playthings and replace the infrastructure as it will benefit all in the end. Concentrate on
industry loss.
8. Little awareness given initially (very poor media). Loss in head means garden hose
pressures about half flow. Positive: water hammer reduced.
9. Washing machine fills slowly – need to help with buckets of water. Washing time is
longer overall. Thanks for what you’re trying to do.
10. I save water wherever I can and I hope others do the same.
11. We’ve got to keep trying!
12. Given that the legal requirement of water pressure is 15m and you are maintaining
35m pressure, it may be worth trialling a 25m pressure to optimise water use further.
13. We have a bore – originally we used the mains (and the high pressure to advantage)
14. Pleased to see that these measures have reduced water consumption and we hardly
noticed.
15. The taste of our water, every week or so, changes flavour! It tastes like ‘metal’ – we
have bought a new kettle and still the ‘metal’ taste continues!!?? Could this be
associated with the trials?
16. We can only use one tap at a time.
17. Not able to comment due to lack of information.
18. The benefits listed in your ad are good and we have overcome the problems but we
may use more water while showering to maintain the heat.
19. Slight drop in pressure at certain times of the day.
20. Less pressure with garden hose – “jet” less effective for squirting cats.
21. Don’t reduce as low as this – an increase would be appreciated.
22. You have already made up your minds and will do it regardless of public comment.
23. Water Corp still have to replace all the pipes – they are very old.
24. Save H2O – a major contributor to saving our environment – we support it.
25. Fix aging leaking infrastructure to save water.
26. Could you please stop doing whatever it is, that makes the water unsuitable for making
a good tasting cup of tea.
27. Every suburb should take turns in reducing water consumption.
28. Water Corporation has failed to maintain an appropriate maintenance/upgrade program
for water supply. Customers have now been seriously affected by the decision to
reduce water pressure.
29. People phone WC and hang up because they are tired of waiting – we tried 3 times.
30. By the very method of delivery (wrapped up in junk mail) many of us would have
missed the opportunity to have a say.
31. Impossible to have shower when washing machine or dishwasher on. Very difficult with
large family home.
32. My ‘pop up’ reticulation system won’t ‘pop’ anymore.
33. We hope the reduction will stop damage to solar HWS – 2 times previously.
34. If there is 16 % loss of water in Rossmoyne it’s about time WC sought out the leakages
and fixed the system. The reduced pressure is not consistent and at times very low. In
fact lower than mine and I have prostate problem.
35. Warn people on ‘mains’ the cost of replacing and reorganising reticulation. Extra
irrigation stations had to be added at great expense to us.
36. Reduced pressure restricts fighting fires – fix the leaks.
24
2010 Water pressure management trial
37. After your water pipe burst on the street lawn it took hours to get it turned off. It left
us with deep sand all over the garden. Bobcat came and damaged our driveway and
then were only allowed to patch the crossover – not impressed.
38. I set up lawn reticulation to cover a certain area with a certain pressure. You have
changed the pressure. Not happy. Do you want to fix it?
39. The Water Corporation should reimburse users for significant costs resulting from
lowering pressure. Surely, repairing the network leaks is the answer.
40. Provide a 1:1 subsidy if things have to be reorganised.
41. My use is well down, however I’m not sure of reason.
42. Obviously a very good idea that should be extended to the rest of the metro area.
43. I never experienced any inconvenience when the pressure was reduced and felt it was a
good thing, as it lessened pressure on old pipes.
44. Good for saving water.
45. I don’t know if such an expansion would affect those areas now experiencing the
optimisation.
46. Water pressure just a bit stronger would be good but benefits (to community) so far
overall cannot be ignored.
47. We live close to the river. I don’t know if that influences the pressure.
48. Less pressure from hose – therefore harder to clean brick paving. Good to read
reduction in water loss.
49. Large fluctuation in hot water when two outlets in use (mains pressure gas – storage).
Dump valve on evaporative aircon did not jam this year! Less water hammer with
pipes.
50. Reduced pressure at rear of property.
51. Hose doesn’t spray with high pressure when turned on to full. If it can reduce leaks
and maintenance on water services then it is worth it.
52. When turning on the water in the kitchen, we get an expulsion of air.
53. At times pressure not enough to fill toilets and makes noise.
54. Had to modify my drip system in to two halves.
55. I have noticed more rusty water flow.
56. Shower temperature seems more difficult to adjust. Cold water pressure seems
stronger than that of the hot water pressure through gas water heater, but only in the
shower.
Overall Summary
219 replies from 3080 customers (7.1% response)
Were you aware of the water network optimisation trials in your suburb?
Yes – 197 (90%)
No – 21 (9%)
Blank – 1 (1%)
If yes, was this from information you received from the Water Corporation?
Yes – 161 (82%)
No – 29 (15%)
N/A – 7 (3%)
25
2010 Water pressure management trial
Have you been affected by the network optimisation trials?
a) Inside your home:
Nil – 103 (47%)
Minor – 55 (25%)
Moderate – 43 (20%)
Major – 18 (8%)
b) Outside your home: Nil – 103 (47%)
Moderate – 36
Minor – 43 (20%)
(16%) Major – 37 (17%)
Have you had to make any changes to your water-using appliances as a result?
a) Inside your home:
Yes – 48 (22%)
No – 171 (78%)
b) Outside your home: Yes – 64 (29%)
No – 145 (66%)
Blank - 10 (5%)
Have you experienced any negative impacts which you believe are the result of
reduced water pressure?
Yes – 104 (47%)
No – 115 (53%)
If yes, please summarise these:
Garden retic – 53
Reduced pressure in taps/shower - 48
Washing machine or dish washer (time to fill) – 14
Hot water system – 8
Toilets (time to fill) – 4
Appliances (High pressure cleaner and water filter) not working properly – 3
Have you experienced any positive impacts which you believe are the result of
reduced water pressure?
Yes – 16 (7%)
No – 193 (88%)
Unsure – 10 (5%)
If yes, please summarise these:
Water use reduction – 8
Less water hammer – 2
Appliances not failing – 2
Doing something helpful -1
Hose fittings not blowing off nowadays - 1
Recommend expansion of Network Optimisation to other areas?
Yes – 149 (68%)
No- 53 (24%)
Undecided – 17 (8%)
26
2010 Water pressure management trial
Comparative summary
Waterford
Rossmoyne
Shelley
Combine
40 (6.2%)
98 (9.8%)
81
(5.7%)
219
(7.1%)
35 (88%)
92 (94%)
70
(86%)
197
(90%)
29 (83%)
79 (86%)
53
(76%)
161
(82%)
23 (58%)
47 (48%)
Minor
33
(41%)
103
(47%)
7
26
22
55 (25%)
Moderate
6
20
17
43 (20%)
Major
4
5
9
18 (8%)
Nil
20 (50%)
52 (53%)
31
(38%)
103
(47%)
Minor
8
16
19
43 (20%)
Moderate
4
19
13
36 (16%)
Major
8
11
18
37 (17%)
Yes
11 (28%)
21 (21%)
16
(20%)
48 (22%)
No
29 (72%)
77 (79%)
65
(80%)
171
(78%)
Yes
14 (35%)
24 (25%)
26
(32%)
64 (29%)
No
24 (60%)
66 (67%)
55
(68%)
145
(66%)
Yes
20 (50%)
42 (43%)
42
(52%)
104
(47%)
No
20 (50%)
56 (57%)
39
(48%)
115
(53%)
Yes
4 (10%)
11 (11%)
1 (1%)
16 (7%)
No
31 (78%)
87 (89%)
75
(93%)
193
(88%)
Yes
28 (70%)
70 (71%)
149
(68%)
No
10 (25%)
18 (19%)
51
(63%)
25
(31%)
Undecided
2 (5%)
10 (10%)
Response rate to survey
Were you aware of the water network
optimisation trials in your suburb?
YES
If yes, was this from information you
received from the Water Corporation?
YES
Nil
Have you been affected
by the network
optimisation trials?
INSIDE
Have you been affected
by the network
optimisation trials?
OUTSIDE
Have you had to make
any changes to your
water-using appliances
as a result? INSIDE
Have you had to make
any changes to your
water-using appliances
as a result? OUTSIDE
Have you experienced
any negative impacts
which you believe are
the result of reduced
water pressure?
Have you experienced
any positive impacts
which you believe are
the result of reduced
water pressure?
Recommend expansion
of Network Optimisation
to other areas?
27
2010 Water pressure management trial
5 (6%)
53 (24%)
17 (8%)
Appendix E – Flow Modulation PRV Settings
Waterford PRV
Flow rate
zero flow
0.2 l/second
20 l/second
40 l/second
Downstream setting
45 metres pressure
37 metres pressure
38 metres pressure
40 metres pressure
Rossmoyne PRV
Flow rate
zero flow
0.2 l/sec
20 l/sec
40 l/sec
45 l/sec
Downstream setting
45 metres pressure
35 metres pressure
39 metres pressure
45 metres pressure
48 metres pressure
Shelley PRV
Flow rate
zero flow
0.2 l/sec
15 l/sec
30 l/sec
28
Downstream setting
45 metres pressure
36 metres pressure
40 metres pressure
46 metres pressure
2010 Water pressure management trial
Appendix F – Capital and Operating Expenditure
Waterford
Total capital expenditure, including project management
Annualised capital expenditure at 6%, 20 year life
Est operational expenditure – comms, audits, monitoring (2.5 hrs/week)
Maintenance expenditure (currently $3790 for 6 months)
$142,558*
$12,430/yr
$8,900/yr
$7,580/yr
Total annual cost
$28,910
* Note: Excludes cost of second PRV which is not needed
Shelley
Total capital expenditure, including project management
Annualised capital expenditure at 6%, 20 year life
Est operational expenditure – comms, audits, monitoring (2.5 hrs/week)
Maintenance expenditure (currently $1450** for 6 months)
$149,008 **
$12,990/yr
$8,900/yr
$2,900/yr
Total annual cost
$24,790
Rossmoyne
Total capital expenditure, including project management
Annualised capital expenditure at 6%, 20 year life
Est operational expenditure – comms, audits, monitoring (2.5 hrs/week)
Maintenance expenditure (currently $1450** for 6 months)
$149,008 **
$12,990/yr
$8,900/yr
$2,900/yr
Total annual cost
$24,790
** Note: Equals 50% of Shelley + Rossmoyne costs, which were not kept separately
29
2010 Water pressure management trial
Appendix G – Derivation of Possible Future Costs and Benefits
Basis of predictions:
Total length of mains in Waterford, Shelley and Rossmoyne
pressure management areas (PMAs)
=
50 km
Total length of mains in Perth
=
13,000 km
Based on distribution of leaks and bursts incidents, assume
30% of Perth mains suitable for cost effective pressure mgt
=
3,900 km
Total leakage saving from trial PMAs (including leaks & bursts)
=
79,890 kL/yr
Total consumption saving from trial PMAs
=
113,600 kL/yr
=
10.6%/yr
Total capex for 3 trial PMAs
=
$440,574
Total opex for 3 trial PMAs
=
$40,080/yr
Assume average size future PMA is same as average of 3 trial areas.
Assume capital and operating costs of future, more difficult PMAs than trial areas, is cancelled
by efficiency gains.
Assume leakage saving from future PMAs is same rate per km as average of 3 trial areas.
Assume consumption saving from future PMAs is sustainable 6% (trial PMAs = 10.6%).
Allow capex $0.5 million and opex $10,000/yr for information system improvement – based on
advice from Information Services Branch
Predictions:
Predicted capex
=
$440,574 x 3900 / 50 + $0.5m
Over 10 years
Predicted year 1 opex
m/yr
=
=
Predicted consumption saving =
=
$3.49 m/yr
=
$0.32
=
$3.23 m/yr
79,890 x 3900 / 50
=
6.231 GL/yr
113,600 x 3900 /50 x 6 / 10.6
=
5.015 GL/yr
=
11.25 GL/yr
Total predicted saving after 10 years
30
$34.9 m
$40,080 x 3900 / 50 / 10 + $10,000
After 10 years
Predicted leakage saving
=
= 6.231 + 5.015
2010 Water pressure management trial