A Cost Comparison for the
Supply and Installation of Three
High Rise Sewer Stack Systems
Published by Studor
Independent Foreword by John Turner
MSc CEnv MCIWEM FIHEEM FCIPHE,
Director of Britewater International Ltd.
www.studor.net
SINCE 1975
Foreword
Years of professional experience have taught me that it is a
real challenge to provide a constructive and comprehensive
cost comparison for any of the building engineering services;
sewer stacks are no different.
Nevertheless, the way in which this study has been
developed in an impartial and detailed manner, using
experienced independent quantity surveyors, designers and
consultants, should give any reader confidence that the
evidence presented is based on standard construction
processes and a practical analysis of the actual costs applied
to each system. In other words, it is a level playing field.
The three systems analysed here are the three most commonly
used approaches for sewer stack design: a Fully Vented
Modified System using AAVs, a Reduced Velocity Aerator
Stack System and a Studor Single Pipe System. However,
there will be hybrids around the world which have been
influenced by local preferences, regulations and experience,
and by individual engineering design exponents.
In an industry that is predominantly price driven it is
encouraging to see what can be achieved by cooperation
between component manufacturers and researchers within
academic institutions. The Studor Single Pipe System
incorporating AAVs and the P.A.P.A. device is the outcome of
such cooperation, and represents a modern, economic,
calculated and researched design approach that can be
consistently reproduced for any building type or height.
BIOGRAPHY
John Turner has over 40 years of experience in the field of
building services engineering, including commercial, public
sector and academic roles. He holds a Master’s degree in
Water and Waste Water Technology and began his
professional career as a Senior Lecturer on the Building
Services course at Salford University in the UK. Since then he
has worked on a wide range of international projects for
some of the most prestigious names in the fields of building
services engineering and the built environment. His posts
have included those of a consulting Senior Public Health
Engineer, a Senior Hydraulics Engineer and a Mechanical,
Electrical and Plumbing Engineer. His experience covers a
comprehensive range of building types including hospitals,
airports, shopping malls, academic institutions, residential
complexes and office buildings.
John is currently based in Manila, Philippines, and is the
Director of Britewater International Ltd. He is a Fellow and
past National President of the Chartered Institute of Plumbing
and Heating Engineering, a Member of the Chartered
Institute for Water and Environmental Management, a Fellow
of the Institute of Healthcare Engineering and Estates
Management and an Associate of the Chartered Institute of
Building Services Engineers. In addition to his commercial
work, he has been a National Examiner for the City & Guilds
course in Plumbing and Mechanical Services, and for the
Chartered Institute of Building Services Engineers technical
paper in Plumbing and Public Health Engineering.
I would recommend that anyone presently engaged on a
construction programme that requires sewer pipework design
and performance assessment should at least consult Studor
and compare for themselves both the economic and technical
advantages inherent in the application and design of their
products.
John Turner
August 2012
www.studor.net
2
SINCE 1975
Introduction
The FVMSS utilises a pipe network that carries air into the
system in order to relieve negative transient pressure whilst
providing a relief vent through which positive transient
pressure can travel, thus directing the transients away from
the water trap seals within the stack system. The FVMSS is
the conventional passive ventilation system, and is the
established requirement for all global plumbing standards.
In 2011 Studor Australia Pty Ltd commissioned an
independent investigation into the costs associated with the
supply and installation, of the three main types of high rise
sewer stack systems currently utilised in Australia and New
Zealand. The system designs were:
1) A Reduced Velocity Aerator Stack System (RVASS).
The SSPS is the only system that employs active ventilation
principles, and uses the working combination of the Studor
P.A.P.A. and Studor AAVs to intercept and alleviate both
positive and negative pressure transients near their source
of generation. This single pipe system was the result of 6
years of academic research carried out specifically to
develop a remedial solution for the issues caused by
transient pressures within high-rise building designs. The
system has rapidly been accepted internationally by
standard organisations and building code bodies, and is
already installed in many of the world’s tallest buildings.
The unique advantage of the SSPS is its ease of installation.
It also is a cost-effective solution for retro-fit, as there is no
need to remove and replace existing pipework.
2) A traditional passive vented system, referred to in this
paper as a Fully Vented Modified Stack System
(FVMSS).
3) The Studor Single Pipe System (SSPS), which by
contrast is an active vented system, incorporating
Positive Air Pressure Attenuators (P.A.P.A.s) and Studor
Air Admittance Valves (AAVs).
The purpose of the investigation was to provide concrete
evidence for something that Studor has long held to be
true; the SSPS is the most cost-effective system on the
market due to its reduced pipework requirements and
quicker, easier installation.
In order to prove this, an independent hydraulics consultant
was asked to design three different stack systems for the
same high-rise apartment building. Each design was based
upon one of the three common technologies (i.e. RVASS,
FVMSS and the SSPS). A bill of quantities for each of the
designs was created and supplied to two separate
plumbing estimators, who were asked to produce estimates
for the supply and installation of the systems.
More about the three systems
The RVASS is a single stack offset system that makes use
of specially designed fittings on every floor to interrupt
the downward flow at approximately 3 metre intervals,
thus preventing the positive and negative transient
pressures from affecting water trap seals in the system.
However, it must be noted that Pressure Relief Lines
(PRLs), must be installed at the base of the stack and at
graded offsets. The RVASS was developed in the 1950s
and has been produced under licence worldwide.
Despite the appeal of having a single stack drainage
system, the use of RVASS in tall buildings in Australia and
New Zealand remains limited in comparison to other
alternative systems.
www.studor.net
The Studor P.A.P.A., a component of the Studor
Single Pipe System
3
STUDOR reserves the right to make changes to the product which may affect the accuracy of information contained in this document
SINCE 1975
Roof
Roof
Open Vent
Bath Tub
Basin
Bath Tub
FD
Basin
FD
Mini-Vent
AAV
WC
WC
Bath Tub
Basin
Maxi-Vent
AAV
FD
WC
Waste Stack
Bath Tub
Aerator Fitting
Basin
FD
Mini-Vent
AAV
WC
Aerator Fitting
Bath Tub
Bath Tub
Basin
WC
FD
Basin
P.A.P.A.
FD
WC
Mini-Vent
AAV
Figure 1. Illustration of a typical RVASS system showing the aerator
fitting at each branch and the pressure relief line at the base of the stack.
FVMSS
Figure 2. Illustration of the Studor Single Pipe System. Note the
lack of both pressure relief line and vent direct to atmosphere.
SSPS
The Project
The building used as the basis for this investigation was
a high-rise apartment block of 22 storeys, referred to as
Hamilton Harbour Apartments. An independent
hydraulics consultant from Brisbane provided three
different designs for the building’s stack system, each
utilising 24 separate stacks:
1) A RVASS system.
2) A conventional FVMSS, incorporating relief
vents. In this case, the consultants designed the
branch ventilation using AAVs, which is common
practise in Australia for this type of system design.
A bill of quantities was created for each of the three
designs and all relevant documents were passed to two
plumbing estimation businesses located in Brisbane.
The estimators were asked to produce estimates for the
supply and installation of each system. To ensure
accuracy, they were asked to provide a per metre /
fitting rate which included the cost of the material and
installation. This allowed for precise costing of each
system down to individual component level.
3) An SSPS, which comprises of the Studor P.A.P.A.
and Studor AAVs.
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4
SINCE 1975
The Estimates
Figure 3. Top section of one of the FVMSS
stack designs used in the study. Note the
secondary vent stack to the left hand side.
Figure 4. Top section of one of the RVASS
stack designs from the study. The offsets
of the aerator fittings are clearly visible.
Each estimate is based on materials and labour costs for
the installation of the stacks and branches. They do not
include:
Two estimates were created according to the following
provisions:
Estimate One
Combination of merchant and generic pricing for
materials
10% margin applied
3% margin applied for stock loss
Labour rate of $75.00 per hour
Material cost for HDPE risers with PVC for branch pipes
(RVASS only)
Material cost for PVC pipe (FVMSS and SSPS only)
Estimate Two
Combination of merchant and generic pricing for
materials
15% margin applied
Labour rate of $75.00 per hour
Material cost for HDPE risers with PVC for branch pipes
(RVASS only)
Material cost for PVC pipe (FVMSS and SSPS only)
www.studor.net
Figure 5. Top section of one of the SSPS stacks
used in the study. Note the location of the
Studor P.A.P.A. device, just below floor level.
5
Delivery charges, crane hire or other costs associated
with materials handling.
Machinery, ladders, scaffolding or other items hired or
used to manufacture or install the systems.
Purchase or replacement of sundry items such as blades,
drill bits or tools.
The PRL at the base of the RVASS stack, which must also
be taken into account when installing this system.
No allowance has been made for design, drafting, fees or
other ancillary costs prior to, during or upon completion of
the project.
SINCE 1975
The Results
The following table shows how the costs supplied by each estimator break down across the 24 stacks
required for each system.
Fully Vented Modified
Stack System
Sovent Stack System
Stack No.
Estimate 1
Estimate 2
Estimate 1
Studor Single Pipe System
Estimate 2
Estimate 1
Estimate 2
1
$
37,749.00
$
37,075.00
$
34,036.00
$
32,855.00
$
31,646.00
$
31,345.00
2
$
38,518.00
$
38,242.00
$
33,999.00
$
33,012.00
$
32,750.00
$
32,447.00
3
$
26,019.00
$
25,833.00
$
24,675.00
$
23,812.00
$
23,740.00
$
23,394.00
4
$
27,171.00
$
26,594.00
$
23,077.00
$
22,034.00
$
18,792.00
$
18,874.00
5
$
26,129.00
$
25,580.00
$
23,173.00
$
22,106.00
$
18,792.00
$
18,874.00
6
$
27,145.00
$
26,851.00
$
22,404.00
$
22,391.00
$
21,258.00
$
21,741.00
7
$
37,030.00
$
37,017.00
$
35,360.00
$
34,748.00
$
33,123.00
$
33,374.00
8
$
38,323.00
$
37,669.00
$
32,114.00
$
31,520.00
$
30,454.00
$
30,488.00
9
$
44,865.00
$
44,257.00
$
42,001.00
$
41,355.00
$
40,694.00
$
40,738.00
10
$
28,312.00
$
27,859.00
$
26,222.00
$
25,984.00
$
24,604.00
$
25,080.00
11
$
46,302.00
$
45,315.00
$
42,035.00
$
40,671.00
$
40,429.00
$
39,716.00
12
$
41,924.00
$
41,546.00
$
34,911.00
$
34,014.00
$
33,277.00
$
33,176.00
13
$
44,918.00
$
44,466.00
$
36,860.00
$
36,260.00
$
35,264.00
$
35,459.00
14
$
38,598.00
$
37,757.00
$
33,370.00
$
32,978.00
$
32,231.00
$
32,497.00
15
$
29,596.00
$
29,330.00
$
28,857.00
$
27,980.00
$
27,226.00
$
27,065.00
16
$
47,577.00
$
46,625.00
$
42,351.00
$
42,148.00
$
40,838.00
$
41,336.00
17
$
8,818.00
$
8,697.00
$
7,264.00
$
6,832.00
$
4,397.00
$
4,418.00
18
$
8,818.00
$
8,697.00
$
7,264.00
$
6,832.00
$
4,397.00
$
4,418.00
19
$
29,844.00
$
29,672.00
$
26,444.00
$
25,636.00
$
25,447.00
$
25,323.00
20
$
29,844.00
$
29,672.00
$
26,444.00
$
25,636.00
$
25,447.00
$
25,273.00
21
$
6,965.00
$
6,753.00
$
6,089.00
$
5,631.00
$
2,954.00
$
3,007.00
22
$
6,965.00
$
6,753.00
$
6,089.00
$
5,631.00
$
2,954.00
$
3,007.00
23
$
34,068.00
$
34,065.00
$
30,553.00
$
29,853.00
$
28,635.00
$
28,566.00
24
$
31,931.00
$
31,682.00
$
26,961.00
$
25,780.00
$
25,602.00
$
24,999.00
SUB TOTAL
$
737,429.00
$
728,007.00
$
652,553.00
$
635,699.00
$
604,951.00
$
604,615.00
GST
$
73,742.90
$
72,800.70
$
65,255.30
$
63,569.90
$
60,495.10
$
60,461.50
TOTAL
Average Price
$ 811,171.90
$ 800,807.70
$ 717,808.30
$ 805,989.80
$ 699,268.90
$ 665,446.10
$ 708,538.85
$ 665,076.50
$ 665,261.30
Figure 6. Summary table showing breakdown of costs for each estimate by system and stack number.
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6
SINCE 1975
The Conclusions
1) The Studor Single Pipe System is the most
cost-effective of the three drainage systems.
A quick analysis of the figures in the preceding section
immediately shows that the SSPS offers the lowest overall
combined costs for supply and installation. In ascending
order, the average cost for each system was:
1. SSPS:
2. Traditional FVMSS:
3. RVASS:
3) Although the Studor Single Pipe System offers
differing levels of savings dependent on the
load, a saving is always made.
In every case, the SSPS, including the P.A.P.A. device,
proved the most cost effective design for any of the 24
stacks. However, we can also see a relationship between
the extent of the savings and the load on the stack.
Please see Figure 7 at the bottom of the page.
$ 665,261.30
$ 708,538.85
$ 805,989.80
4) The Studor Single Pipe System is the easiest
system for contractors to cost accurately.
Calculating the standard deviation for each set of estimates
provides us with the following results:
This means that the cost of supplying and installing the
SSPS would be 6.11% lower than the cost of the FVMSS
and 17.46% lower than the cost of the RVASS.
Furthermore, we can confidently state that the total cost for
the installation of the RVASS would also be slightly higher,
since neither estimate included the labour and materials to
install the pressure relief line at the stack base as required.
1. SSPS:
2. RVASS:
3. Traditional FVMSS:
As we can see, the estimates for the SSPS show the lowest
standard deviation, followed by the RVASS and finally the
FVMSS. The connotation is that, due to the straightforward
system design and its ease of interpretation, the contractors
were able to create more accurate and representative
estimates for the supply and installation of the SSPS. This
degree of consistency obviously has real-life advantages for
contractors who install drainage systems based on Studor
technology; the likelihood of projects running over-budget
will be significantly lower than with the other passive
drainage systems, and the provision of consistent and
reliable quoting makes it easier for them to manage their
own cash flow, as well as to secure long-term
enhancements to both their profitability and their
reputation.
2) Specifying the complete Studor Single Pipe
System, including the P.A.P.A. device, creates
additional savings on top of those offered by Air
Admittance Valves.
A point worth noting is that the traditional Fully Vented
Modified Stack System (FVMSS) design, whilst
incorporating a relief vent, utilises AAVs where required in
place of traditional “branch” or “group” vents. This means
that the additional savings offered by the SSPS are a direct
result of specifying the P.A.P.A. device. This saving can be
attributed to the P.A.P.A. alleviating the need for extra
pipework required for relief, stack and header vents on the
FVMSS, as well minimising the number of roof penetrations
required, thereby reducing both labour and materials costs.
An additional benefit of not having a relief vent with the
SSPS is that the duct can be reduced in size, providing the
possibility of increasing the habitable space of the building.
Average Cost of RVASS
$
261.34 (0.04%)
$ 7,328.60 (0.91%)
$ 13,109.34 (1.85%)
Average Cost of FVMSS
Average Cost of SSPS
Average SSPS Saving
High Load
$ 47,101.00
$ 42,249.50
$ 41,087.00
$ 4,435.50
Low Load
$
$
$
$ 3,495.25
8,757.50
7,048.00
4,407.50
Figure 7. Table showing relationships between SSPS savings and the load on the stack.
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7
SINCE 1975
Summary
The results of this investigation have demonstrated that the
SSPS, including the P.A.P.A. device, is the most economical
of the three drainage systems commonly utilised for
high-rise developments in Australia and New Zealand.
Whilst the extent of the savings that can be achieved is
dependent upon the precise design of the stack, the SSPS
is invariably the most cost-effective of the three options.
Further Information
Additional information in relation to this study, including a
complete breakdown of all estimates, will be made
available to interested parties upon request.
Please contact the Studor Sales and Technical Support
Centre on +44 845 601 32 92 or by email to
[email protected].
Naturally, the costs associated with the investigation were
estimated in Australian Dollars; however, the relative costs
of the three systems are likely to be broadly similar across
a number of other markets, including the UK and Europe.
Furthermore, because of differing plumbing regulations, it
is likely that in these territories an active drainage system
based on Studor technology would require fewer P.A.P.A.
devices, thereby creating even greater savings in
comparison to the costs of the other passive drainage
systems.
In addition to being the most cost effective of the three
drainage systems investigated, the SSPS also offers a
number of other benefits. The lack of roof penetrations
makes it ideal for buildings requiring a strong external
aesthetic appearance, the reduced pipework requirements
make it a more sustainable choice in terms of raw
materials used, whilst the reduction in duct size provides
the possibility of generating additional income from an
increased habitable space.
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SINCE 1975
0993-0001/112012