Regulatory Impact Assessment (RIA)
Part G (Hygiene) of the Building Regulations
Proposed requirement for Dual Flush Toilets
November 2006
Section 1: Context
1.1 Policy Context
Despite the plentiful rain we experience in this country, fresh water is not an infinite resource.
On a global scale, usable fresh water accounts for only 3 % of total water resources, the other
97% of the world’s water is saline or seawater and therefore not suitable for drinking.
As Ireland’s population increases so does its demand for water. This results in increased
amounts of water being extracted from our rivers. This can have a negative effect on the local
ecology.
Once the water is extracted, it requires treatment in order to make it suitable for consumption.
Treatment generates demand fir the production and distribution and storage of certain
chemicals e.g. chlorine. The treatment process costs approximately €1.00/m3 1.
Energy is needed to treat the water, to deliver it to the end user and then re-treat it as
sewage. This energy usage adds to the volumes of CO2 emitted in Ireland and this, in turn,
contributes to the global problem of climate change. Ireland may as a result of climate change
experience higher rainfall in winter and associated flooding along with lower summer rainfall
resulting in water shortages. This may make it more difficult to meet the increased demand for
drinking water.
2
According to the European Environment Agency, the average consumption for all
households’ purposes in the EEA is about 150 litres per capita (1999) 3. On this basis the
average water consumption per person in Ireland comes to a staggering 55,000 litres per
person per year. The third biggest user of water is the WC, accounting for almost 35% of a
person's average daily water consumption.4
1
This is the average cost for abstracting, treating and distributing drinking water to consumers; it also includes
treatment and disposal of treatment by-products. It excludes the cost savings that arise from the reductions in
wastewater volumes that require treatment. The figure does not take into account the capital costs of building the
facility or the administrative costs associated with operating it, which would arise in any case. Source: Water
Services, DOEHLG
2
http://www.taptips.ie/in-the-house.htm
3
http://themes.eea.europa.eu/Sectors_and_activities/households/indicators/energy/hh07household.pdf
4
Water Services Investment Programme, DOEHLG
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1.2 Regulatory Context
Part G (Hygiene) of the Building Regulations 1997 sets out the legal requirements for sanitary
installations. At present, it requires that adequate sanitary conveniences be provided in a
building. Technical Guidance Document (TGD) G advises on the scale of provision, the siting
of appliances and their design and installation. TGD G refers to the Irish Standard
(I.S.) 70:1980: “Water Closet Cisterns for Domestic Use”. This standard covers WC flushing
cisterns with discharges of 9 (+or -0.5) litres, or in the case of a dual flush 5, a short flush of
4.5 (+1 or –0) litres.
Under the Local Government Act 1994 (No.8 of 1994), Dublin City Council published a
revised set of byelaws in 2003. These limited the maximum flush volume to 6 litres for both
new and replacement WCs in buildings. This has influenced the marketplace in so far as
many WCs sold today are 6 litres. However, these bye-laws only apply in Dublin City
whereas the Building Regulations apply nationally.
The draft Part G Regulations and related TGD G propose a maximum flush volume of 6 litres
and a reduced flush volume no greater than two thirds of the maximum (maximum 4 litres) in
all new buildings and when WC are being replaced in existing buildings.
Dual flush toilets are being voluntarily installed as the norm on most modern commercial
buildings demonstrating the water saving advantages of dual flush are accepted in the market
place.
Mr Dick Roche, TD, Minister of the Environment, Heritage and Local Government announced,
during an Oireachtas debate on the Water Services Bill, that he intended to make dual flush
toilets mandatory under the Building Regulations.
1.3 Statement of objectives
General objectives:
 Conservation of Water- a precious natural resource

Optimisation of Capacity- of existing piped water supply systems, and thereby defer need
to invest in the augmentation of existing supplies.

Conservation of Energy - energy is the greatest cost in producing drinking water

Reduced demand for Chemicals- required for the treatment of potable water e.g. Chlorine

Cost Savings - to local water services authorities and commercial water users
5
Dual flushes are flushing cisterns with two modes of operation, one delivering a larger volume than the other. The
full flush is designed to remove solids and paper and the reduced flush to remove urine. They act as water saving
mechanisms as only one out of five visits to the WC warrants a full flush.
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Immediate objective:

Ensure that all WCs in new buildings and replacement WCs in existing buildings are dual
flush, in order to reduce the volume of water used.
Section 2: Cost Benefit Analysis
2.1 Assumptions
The cost benefit analysis below is based on the assumption that users understand and know
how to use dual flush toilets correctly.
Dual flushes are flushing cisterns with two modes of operation, one delivering a larger volume
than the other. The full flush is designed to remove solids and paper and the reduced flush to
remove urine.
They act as water saving mechanisms as only one out of five visits to the WC warrants a full
flush. 6 It is estimated that 5 flushes are made per person per day.
7
The analysis is based on new domestic buildings only, as many commercial premises are
already using them.
The cost of water treatment is estimated at €1.00/m 3. This is the average cost for abstracting,
treating and distributing drinking water to consumers; it also includes treatment and disposal
of treatment by-products. It excludes the cost savings that arise from the reductions in
wastewater volumes that require treatment. The figure does not take into account the capital
costs of building the facility or the administrative costs associated with operating it, which
would arise in any case.
The economic value of the reduction in the demand on our national water resources- rivers,
lakes and underground sources- cannot be estimated but is one of the biggest benefits of
dual flush toilets
2.2 Analysis
Per WC
A survey of 15 suppliers in the greater Dublin area was carried out. The results are presented
in Table 1 below.
6
Nick Grant and Mark Moodie; WCs; best practice since the Water Fittings Regulations 1999. Elemental Solutions
and also Environment Agency, UK
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In general the prices for bathroom suites vary considerably from basic to high end. This
survey focused on the low to middle range.
Findings:

The price of a basic dual flush toilet is on average 0% to 30% (approx) more expensive
than an equivalent single flush toilet.

Dual flush toilets are available in most ranges.

Within a range that has both dual flush toilets and single flush, often both are the same
price.
It is clear from the findings that some manufacturers are charging a premium and others not
for dual flush toilets. Should they become standard practice for new and replacement
installations, market forces are likely to create a situation where there is little or no difference
in price.
Nationally
Table 2 below shows the daily usage of water for flushing per household using single and
dual flush toilets.
The single flush figures are based on 9litre, 7.5litre and 6litre cisterns. This is due to the fact
that some existing houses will have these bigger volumes. Others will have been renovated to
incorporate lower volume flushes and most new houses (since 2003 at least) will have 6 litre
cisterns.
The dual flush figures are based on the most common 6/4litre model used in the ratio of 4 low
flushes (4litres) to 1 full flush (6 litres).
Table 3 highlights the water savings between single flush of 9, 7.5 and 6 litre and the 6/4 dual
flush. The reductions are 51%,41% and 27% respectively.
This translates into between 2 billion and 700 million litres of water savings per annum.
Reductions in water usage such as these are valued between €2 million and €700,000.
7
http://www.environmentagency.gov.uk/commondata/103196/876806?referrer=/subjects/waterres/286587/286599/286911/548861/862887/
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Realistically, with the prevalence of 6 litre cisterns on the market and the high number of
renovations in the domestic market it is likely that savings will be nearer the lower end of
these ranges ie 27% savings, 700million litres and €700,000 per annum.
The capital cost of constructing 2 to 4 standalone new treatment plants to provide a total of
700 million litres/year would be in the order of €2.8m to €3.4m ( for 5 to 8 standalone plants to
provide 2 billion litres/year would be in the order of €5.8m to €7.5m). If the capacity was to be
provided by extending existing plants, the cost would be between 50% to 70% of these
ranges.8
8
Water Services Investment Programme, DOEHLG
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TABLE1: Survey of Dual Vs Single Flush Toilets - June 06
Manu.
Range
Flush
Manu 1
X
Y2
Z1
Z1
Single
Dual
Single
Dual
A
B3
C4
Single
Dual
Dual
Manu 2
Supplier 1 Supplier 2 Supplier 3 Supplier 4 Supplier 5 Supplier 6 Supplier 7 Supplier 8 Average
Price
125
150
176
176
195
195
160
325
105
129
200
175
180
250
170
130
118
105
105
135
176
165
208
Average %
Difference
between Single
and Dual Flush
115
150 31% Increase
176
176 54% Increase
159
261 64% Increase
170 7%Increase
Notes:
1. Z is a low - middle range product from Manu 1
2. Y was a little cheaper than Z but it wasn’t widely used - hence little price information
3. B is a middle range product from Manu 2 but yet the most common
4. C is cheaper than B but not widely used - hence little price information
5. Manufacturer 1 & 2 have approximately 50% of the Irish market
Manu.
Manu 3
Misc
Range
Flush
Single
Dual
Single
Dual
Supplier 9 Supplier 10 Supplier 11 Supplier 12 Supplier 13 Supplier 14 Supplier 15 Average
Price or
Range
170
240
160
160
186 199-400
300 199-400
77
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190 319-400
356 302-400
Average %
Difference
between Single
and Dual Flush
165
200
21% Increase
77-400
199-400
0-150% Increase
TABLE 2: Daily usage of water for flushing per household using single
and dual flush toilets
1. Single Flush Toilets:
Volume of Flush (litres)
No of people per household 1
No of flushes per day 2
Daily usage per
household using single
flush (litres)
9
3
5
7.5
3
5
6
3
5
135
112.5
90
Note 1: Housing Policy, DOEHLG; Note 2: Environment Agency, UK
2. Dual flush Toilets:
Volume of High Flush
Volume of Low Flush
Volume of flush in No. of people per Ratio of flushes Litres
household
Option 1
6
3
1
4
3
4
Daily usage per
household using dual
flush (litres)
66
TABLE 3: Water savings
Option 1: Ratio of low to high flush usage 4:1
9 litres
7.5 litres
6 litres
Daily usage per household
using single flush
135
112.5
90
Daily usage per household
using dual flush
66
66
66
Daily water savings per
household
69
46.5
24
51%
365
80,000
2,014,800,000
1.00
€2,014,800
41%
365
80,000
1,357,800,000
1.00
€1,357,800
27%
365
80,000
700,800,000
1.00
€700,800
%Reduction
Annual water savings
Treatment Costs
Value of annual water savings
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Litres
New houses pa
Litres
€/m3