BRE014 - Code water calculator update 2009 changes 16 03 09 _2

Code Water Calculator

Update

BRE Global - March 2009

Project Number: BRE014

For: Communities and Local
Government

1

Issue change summary

Date
Version
Issued by
For
Info.
18/02/09
Rev 1
GS
JH
First draft
discussed at
stakeholder
meeting
18/02/09
17/03/09
Rev2
GS
JH
Final version
issued

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Contents

1.  Summary
2.  Introduction
3.  Overview of changes
4.  Quick wins for inclusion now
5.  Potential actions needing further consideration
6.  Issues put on hold
7.  Normalising the use factors
8.  Use factors
9.  Examples of compliant specifications

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1.  Summary
Following Faber Maunsel ’s review of the Code for Sustainable Homes Water Calculator (herein
referred to as the Code Water Calculator), this report outlines BRE Global’s changes applied to the
Water Calculator, based on an analysis of Faber Maunsel ’s review and from BRE Global’s technical
expertise in this area.
It is important at this point to take a step back and look at the key issues that this review set out to
address.  The main issues with the Water Calculator are:
•  The Code Water Calculator is currently overestimating water consumption
•  The overestimation is causing difficulties with achieving the Code Water targets leading to
the use of fittings that are not acceptable to users and in some cases compromise design
quality
The review of the Code Water Calculator needs to result in the production of a revised Calculator
that estimates water consumption in line with average UK consumption levels of 150 litres per
person per day.  It also needs to ensure that the range of fittings required to meet each level are of
an appropriate level of water efficiency.  Its current status results in a limited number of sanitary-
ware options in order to meet the defined targets.  This is having a negative impact on those trying
to meet the Code for Sustainable Homes (the Code) target levels leading to the industry perceiving
the Code water methodology as being a flawed and potential y damaging the Code’s reputation
and uptake.
From the 27 recommendations made by Faber Maunsell, a total of thirteen recommendations are
proposed to be included as quick wins in the Water Calculator or supporting documents (e.g. part
G or the Code technical guide).  Seven further issues could potential y have been included at this
time however additional work is required and given the short timeframe (final report received from
Faber Maunsel  on 06/02/09 and that Ministerial sign off is required on 4th March.  There is insufficient
time to carry out the additional necessary work for inclusion at this time.   This does not mean that
we do not support all such changes and therefore actions have been identified to indicate what is
needed in order to include these changes.  The remaining issues cannot at this present be included
in the current amendment of the Calculator or are issues to take on board for future updates of the
Water Calculator.
The proposed changes suggested for action now are those that meet a defined set of objectives in
order to address the key issues with the Code Water Calculator, highlighted in Faber Maunsel ’s
review, taking into account BRE Global’s experience of such issues from managing the Code.
These issues are considered to need either none or minimal further work in order to include them in
a revised Code Water Calculator with immediate effect.  The impact of the quick wins has been
analysed in Section 7, Example Specifications.
Table 1 summarises what will and wil  not be included in the Code Water Calculator at this time.

2.  Introduction
2.1   Background to the Code Water Calculator
The Code Water Calculator was developed in January 2007 to provide a mechanism for assessing
the water efficiency of new homes against target performance levels set out in ‘Code for
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Sustainable Homes: A step-change in sustainable home building practice’.  In ‘The Future of the
Code for Sustainable Homes – Making a Rating Mandatory: Summary of Responses’, Nov 07, the
consultation feedback indicated that a majority of consultees agree that a whole house
assessment methodology was the preferred option compared to the use of set performance
targets for individual fittings.   The outcome of the review carried out by Faber Maunsell recognised
alternative approaches used international y but found that a whole house method was a
reasonable approach to take.  The review highlights a number of major issues with the Calculator
method and the changes highlighted in this report go a long way to addressing the majority of
issues or highlight the way forward for addressing these in the future.
The Code Water Calculator was based on BRE’s EcoHomes Water Calculator that was first released
as part of EcoHomes in 2000 and subsequent versions, but the methodology was first developed for
BRE’s Office Toolkit, published in 1995.  In order to adapt the BRE Water Calculator for the purposes
of the Code for Sustainable Homes, a revised version of the Code Water Calculator was put
together by the Environment Agency (EA) to support the EA’s ‘The Cost of Compliance with the
Code for Sustainable Homes, UC7231’.  This included updating the Calculator to al ow the use of a
much greater range of fittings with use factors largely derived from the Water Research Centres
CP187.  The BRE Water Calculator was then updated in accordance with this and the methodology
was then written into the Code Technical Guide by BRE Global on behalf of Communities and
Local Government.
In developing the Code Water Calculator, a key consideration was the fittings required to meet
each level of the Code.  The type of fittings required and level of performance were agreed
through a stakeholder group including DEFRA, EA, BRE, BSRIA, CLG, DTI, Housing Corporation and
English Partnerships (the latter two organisations now form part of the Homes and Communities
Agency).  The agreement between stakeholders was that the levels should achieve the following
levels of performance:
CSH
Per capita
Level of performance
Levels  consumption
1 & 2
120
The use of a combination of fittings better than
litres/person/day
current practice or regulator minimums
3 & 4
105
The use of best practice readily available water
litres/person/day
efficient fittings, without the need for water recycling
5 & 6
80
The use of advanced best practice water efficient
litres/person/day
fittings combined with the use of water recycling

There was also an agreement between stakeholders that the Code should be flexible in its
approach as to how homes are designed to meet the target performance levels.  It was agreed
that it should not cause a ban on water consuming items such as power showers, although agreed
that it should not be easy to comply with the higher levels of the Code.  Whilst such items do have
a detrimental effect on water resources, a policy decision was made that it is not the Codes place
to effectively ban these items.  However, where such items are desired and if the homes are to
achieve a Code rating, the homes need to be designed to offset such high consuming items by
specifying other fittings that are much more efficient, or the use of rain and/or greywater.
2.2  Aims of the Water Calculator
The aim of the Code Water Calculator is to provide a method for assessing the water efficiency of
homes taking into account their whole house performance.  This is in the context of government
policy to make a step change in water efficiency to aid water demand management and both
current and future concerns over the availability of water resources.  A secondary aim was also to
stimulate market growth in innovative water efficient fittings.
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2.3  Current status of the Code Water Calculator
The Code for Sustainable Homes has been in place now for nearly 2 years and in this time there has
been significant feedback on issues with the Water Calculator and problems that it is causing in
relation to achieving the Code Water targets.  The main problem is the smal  selection of fittings
available that wil  achieve the water targets particularly for Code level 3.  Evidence presented in
Faber Maunsells’ review of the Code Water Calculator indicates that the fittings required are
pushing beyond the limits of user satisfaction.  There is also evidence of a number of other issues
such as the Calculator leading to poor design and so called ‘game playing’.  This is in relation to
where the methodology al ows offsetting of fittings against one another which may not always lead
to the most sustainable solution.
Whilst it is agreed that the current Calculator is leading to a number of undesired outcomes, the
majority of issues are a result of the fact that the Calculator is overestimating consumption leading
to some rather drastic measure to achieve the targets or elements of ‘game playing’ as described
above.  Bringing the Code Water Calculator back into line with typical water consumption levels
should eliminate such issues.  It is however important to ensure where there is a risk of such elements
of game playing and areas where the Calculator is having a negative impact on future occupants
and overal  sustainability, that these issues are addressed in the review.
From the expert group workshops carried out as part of the review it was evident that the water
Calculator is also being used for purposes beyond for which it was intended.  This includes use of
the Calculator as a tool to assist with water demand management and as a design guide to
determine the fittings to specify for a home.  The overestimated consumption calculated by the
Water Calculator has led to the specification of fittings based on meeting the targets, rather than a
balance between the fittings meeting water efficiency requirements and the functional
requirements of the users.
Having now gone under a major review and with the imminent launch of the Part G consultation
and Code April 09 update, it is essential that changes should be made to the Calculator to address
the current issues.
This report sets out BRE Global’s recommendations for updating the Code Calculator based on our
assessment of the recent review of the Code Water Calculator by Faber Maunsel .
2.4  Update Objectives
Whilst it is critical to ensure current issues with the Calculator are addressed, the recommendations
set out in this report fol ow a set of objectives to ensure that a consistent approach is fol owed as to
the justification for such changes.  It is also important to try and minimise the changes made to the
Calculator, focusing on addressing the most significant issues to minimise the potential impact on
the assessment process, manufacturers and specifiers.  As part of this, ensuring the Calculator can
remain a simplified method is a key consideration, particularly due to potential impacts on the
current Code assessment process and the Calculators incorporation into Part G.  The changes to
be made are based on recommendations set out in Faber Maunsel ’s review of the Code Water
Calculator plus any additional issues suggested by BRE’s code technical team.  In order for such
recommendations to be taken forward, they must adhere the fol owing objectives:
1.  Be based on a scientifically robust evidence al owing changes to be defended and
ensuring changes correspond to existing research, where this is not possible, any
assumptions made, should be clearly stated and transparent;
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2.  Consider the impact on a non technical audience in interpreting the assessment method
minimising complexities where possible;
3.  Consider the broader policy objectives of the Calculator in reducing water efficiency and
driving innovation;
4.  Take into account the impact on product manufacturers and specifiers;
5.  Consider the impact on both the Code for Sustainable Homes and Part G;
6.  Take into account impacts on auditing through the Code.
7.  Feasible to action (in line with above objectives) in the time available
Where recommendations have not been included as issues to be actioned now, this wil  related to
the fact that they do not meet the above set of objectives.  The report details issues which prevent
the change from being made and what would be needed to address such issues.  If an issue is not
to be included in this update, it does not mean that BRE necessarily disagree with the principle of
such changes, to the contrary, a large majority of the proposals made BRE is in support of.  There
may however be further work required in order to ensure such changes proposed do not have
negative impact and to justify the changes with further evidence.
As changes to the Calculator can have such considerable impacts, more so now with it supporting
part G, the above approach aims to give confidence in the decisions made about the
recommendations being adopted and the method for doing so.
3.  Overview of changes
Table 1: Changes for inclusion within the Water Calculator

Key:

For action

Further research

Issue on

Calculator review
now
needed, not for
hold
process issue
inclusion now

Item  Recommendation
Priority
Next stage
Ref.
001
Establish Code Water principles and
Action now
Establish principles and
Calculator objectives
objectives for inclusion in
Calculator where possible.
002
Modify Calculator results for typical
Action now
Compare revised Calculator
sanitaryware  is 135 – 150 litres/person/day
to typical consumption,
consider normalisation factor
where significant difference
remains.
003
Modify Calculator algorithms to reduce
Action now
Amend Calculator with fixed
water savings scope
use volumes for taps which
limits the impact of reduced
flow rates to a more realistic
level.
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004
Introduce limits to design flexibility to
Action now
Add recommended
maintain functionality and user
minimum flow rates to the
acceptability
Code in line with BS6700:2006
(Design, instal ation,
testing and maintenance
of services supplying
water for domestic use
within buildings and
their curtilages –
Specification), 5.3 Hot Water
Services, Commentary and
recommendations on 5.3.2.
005
Establish a Code Water technical review
Issue for future
Add to list of considerations
mechanism
Calculator review
for future Calculator revisions
process
006
Revise Calculator algorithms to include
Action now
Add percentage of use
average flow intensity for shower and
factor to Calculator using
reduce the average flow intensities for taps
assumptions made from
from the current 2/3 ‘use factor’
analysis of WRc CP337.
007
Revise Code Water Calculator algorithms to  Further
Pending further research to
include non-linear average flow intensity for  consideration
demonstrate actual
showers
needed, not for
evidence
inclusion now
008
Ensure current and future Code Water
Issue for future
Add to list of considerations
Calculator revisions account for micro
Calculator review
for future Calculator revisions
component study methodology when
process
adopting or deriving factors for use in
Calculator algorithms
009
Update frequency and duration of use
Action now
Incorporate updated use
factors used in Code Water Calculator
factors, obtain references
algorithms based on WRc CP337
from WRc CP337, merge
frequency, duration and
percentage of use factors
into one use factor to simplify
calculation method.
010
Remove bidets from the Code Water
Action now
Remove from Calculator
Calculator
011
Use weighted averages in Water Calculator  Further
Include proposed method as
algorithms for design flow rate for multiple
consideration
outlined in this report.
taps, showers and fil  volumes to overflow for  needed, not for
Calculator sensitivity analysis
multiple baths.
inclusion now
required.
012
Revise Code Water Calculator algorithms
Action now
Add fixed usage for kitchen
for basin taps and kitchen sink taps to
sinks based on DEFRA future
include fixed proportion of water use
water.  Consider adding
factor for wash hand basins.
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013
Improve Code technical guidance on
Action now
Provide improved instructions
Calculator inputs for mixer taps, separate
in Water Calculator based
hot and cold water taps and showers with
on existing text in code
multiple flow rates
technical guide
014
Revise Code Water Calculator algorithm for  Further
Pending analysis of
water softeners to include al  water uses
consideration
Calculator sensitivity.
supplied by the water softener and to
needed, not for
derive regeneration frequencies based on
inclusion now
Research updated
daily demand for softened water
Calculator algorithm for
water softeners.
015
Review the role of grey and rainwater
Issue on hold
Not to be included as part of
systems in meeting Code Water levels
Calculator update.
016
Revise Code Water Calculator algorithm for  Action now
Update Calculator
rain and greywater based on the new British
methodology for rainwater
Standards
based on BS8515:2009
017
Establish a water hierarchy to guide
Further
Add to list of considerations
ongoing development of the Code
consideration
for future Calculator revisions
approach to water efficiency
needed, not for
inclusion now
018
Move to Calculator inputs based on
Further
Review method used to
measurement or best estimate of
consideration
determine site pressure.
site/system water pressure
needed, not for
inclusion now
Gauge impact on
manufacturers.
019
Consider applying an occupancy factor to
Issue on hold
Not to be included as part of
the Code Water Calculator figure for
Calculator update.
household water demand
020
Limit al  Calculator inputs and outputs to
Further
Pending analysis of
values rounded to nearest 0.5 litres
consideration
Calculator sensitivity.  This
needed, not for
also has potential impacts
inclusion now
where the Calculator is to be
included in an Excel based
format as Excel does not
allow rounding to the nearest
0.5.  Set the Calculator to 1
decimal place for the time
being.
021
Add waste disposal units in line with revised
Action now
Add waste disposal units to
Part G
Calculator.
022
Consider adding external water use to align  Action now
Add additional row to
Code Water Calculator results with results for
indicate external water use
the Part G Calculator
and total consumption
figures for both Code and
part G purposes.
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023
Add an allowance for leakage to the Code  Issue on hold
Not to be included as part of
Water Calculator and consider including an
Calculator update.
equivalent saving for specification of leak
detection and avoidance measures
024
Undertake a scoping study to determine
Issue for future
Add to list of considerations
relative impacts of microcomponents of
Calculator review
for future Calculator revisions
water use and saving measures not
process
currently included in the Calculator or
addressed in the Code methodology.  Use
this as the basis for planning for the
expansion of the Calculator scope in future
revisions.
025
Expand and improve Code Water technical  Action now
Add any further useful
guidance
references to good design
advice and water efficiency
best practice where
practical.
026
Involve stakeholders in regular reviews of
Issue for future
Add to list of considerations
the Code Water Calculator
Calculator review
for future Calculator revisions
process
027
Review higher target levels of the Code and  Issue on hold
Not to be included as part of
relative spacing of the targets along with
Calculator update.
the range of water efficiency options
currently available to meet each target
level

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4.  Quick wins for inclusion now
From the recommendations set out in Faber Maunsell’s report, the fol owing are those issues that
BRE Global suggests should be incorporated into the review of the Code Water Calculator as quick
wins.  These issues are those that meet the objectives set out in this report and changes that can be
made in the timescale available.  It is recommended that these changes should be made to the
Water Calculator now for the version used for Part G and the April 2009 version of the Code.  The
impact of these changes on the Code Water Calculator has been il ustrated in section 7, Example
Specifications.  This indicates the impact of the changes and the fittings that can now be used to
achieve the Code Water targets.
4.1
Item Ref 001: Establish Code Water Calculator principles and objectives
BRE Feedback
It is important to maintain users expectations of the Calculator’s purpose to ensure this is
understood and we recommend such principles are considered for inclusion.   The purpose of the
Water Calculator is to assess the water efficiency of new homes against a set performance target.
Water efficiency is assessed in the Calculator by looking at the contribution each fitting has on
household water consumption, based upon normalised use factors established from research on
typical water consumption in new homes.

Recommended action
•  Review principles established from the Faber Maunsel  report.
•  Add detail to CSH technical guide and draft text for Part G.
4.2
Item Ref 002: Modify Calculator so results for typical sanitaryware is 135-150
litres/person/day
BRE Feedback
The recommended action from Faber Maunsel  is to modify the algorithms within the Calculator so
that there is a reasonable statistical correlation between calculated results comparable to typical
UK consumption.

BRE agrees that this is needed to ensure that the Calculator is proportioning relative water
consumption for each fitting to a level comparable with typical consumption.  This is to ensure that
the impact of each fitting on overal  water efficiency is assessed correctly.  It is also to address a
key criticism of the Code Water Calculator so that the results presented by the Calculator show
such a correlation with typical use.

Modifications to the use factors in the Calculator should be limited to changes that can be
supported by evidence so that changes made are based on robust data and can be defended
when questioned.   As the evidence base is quite limited, there is a risk that modifying the
Calculator may still not achieve a reasonable statistical correlation with typical use.   To establish
whether this is the case, the Calculator has been tested against typical UK consumption to identify
how the amended Calculator correlates with typical use as il ustrated in Annex 1.  This has been
done by comparing the calculated use of typical UK fittings with the typical UK consumption per
person from Ofwat data.  The illustration shows that whilst the use factors within the Calculator have
been updated using the latest research (as per recommendation 009), the Calculator is still
overestimating water consumption compared to typical UK consumption.

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Recommended action

Recognising the limited potential for achieving a reasonable correlation with typical UK
consumption, in order to fulfil the recommended action, a normalisation factor is recommended in
order to calibrate the calculated use in line with typical use.   This is purely a presentational issue to
adjust the calculator so that it shows a closer relationship between calculated consumption and
average UK water consumption.

The normalisation factor is based on the percentage difference between calculated results for
typical fittings and measured results for UK consumption.  The normalisation factor is derived as
follows:
Normalisation factor  =    Measured typical UK consumption
                                             Calculated consumption for typical fittings
Where:
Measured typical UK consumption = 150 litres/person/day
Calculated typical UK consumption = 165 litres/person/day
Normalisation factor = 0.91

The normalisation factor assumes a typical fitting specification based on anecdotal evidence of
the typical fittings in the UK.  The use of a typical fittings specification has been used in several
areas of the Calculator algorithms proposed by Faber Maunsell such as determining the
percentage of flow rate for taps and also in calibrating the Calculator against typical
consumption.

Applying a normalisation factor can be seen as a means to openly recognise that the Calculator
has a degree of inaccuracy compared to typical consumption and shows that this has been
recognised and taken into consideration in the Calculator.  This is to show that calculated
predicted use has been brought in line to better reflect actual use.

4.3
Item Ref 003: Modify Calculator algorithms to reduce water savings scope
BRE feedback
This issue is addressed in point 4.8, Item Ref 012, by setting a fixed proportion of use for basin and
kitchen taps.
4.4
Item Ref 004: Introduce limits to design flexibility to maintain functionality and user
acceptability
BRE Feedback
This is one of the key criticisms of the Code and it is recognised that this needs to be addressed to
reduce the impact on home owners and to maintain the reputation of the Code and not damage
the potential uptake of the Code.

The suggestion that a Code technical review board could review situations where flexibility to these
limits can be al owed is questionable, particularly related to limits defined by BS6700.   A minimum
capacity WC should not be set but the requirement should be that the WC meets BS EN997:2006 for
Class 2 WC suites.  The bath size suggested does not appear to be related to a specific standard
and including this would be hard to justify and also situations where a more intelligent bath size of a
smal er capacity could still meet user satisfaction.

Recommended action
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Add recommended minimum flow rates into the Code technical guide in line with BS6700:2006, 5.3
Hot Water Services, Commentary and recommendations on 5.3.2.  This is to tackle the issue of the
specification of fittings that do not meet minimum user satisfaction levels.  Consideration needs to
be given as to how this can be taken account of in part G.

CLG may need to review the impact on manufacturers that produce fittings of a lower flow rate
than those set as minimums however including the flow rates as recommended rather than
required would make this less of an issue.  This issue is further looked at in part 9 of this report which
looks at fundamental issues which would be created where minimum recommended flow rates are
not included.

4.5
Item Ref 006: Revise Calculator algorithms to include average flow intensity for showers and
reduce average flow intensities for taps from the current 2/3 use factor

BRE Feedback
The 2/3 factor for taps was introduced as a short-term approach to adjust the rates so they better
reflect typical tap use.   This was a fair assumption that users wil  not use taps at the ful  flow rate all
the time.  The assumptions made in the recommendations from Faber Maunsell and the basis of this
has been analysed and seems sensible and we suggest this should be adopted as it is based on
analysis of the new WRc CP337 identiflow research.
In relation to showers, the proposed method for accounting for non linearity in shower flow rate is
not based on any specific research and therefore cannot be included as part of a revised
Calculator. Whilst the average flow rates indicated are based on a Market Transformation
Programme publication (BN DW Shower: Actions to improve shower design and efficiency - Briefing
Note relating to Policy scenario objectives in Policy Brief), the maximum design flow rates assumed
have no evidential basis and therefore the non linearity relationship is an assumed one rather than
an evidence based theory.    Insufficient evidence has been provided to demonstrate that there is
a non linearity between design flow rate and actual flow rate in order to account for this issue at
present.
Recommended action

Incorporate the updated average flow intensities for taps based on WRc CP337.
Add the non-linear relationship of average shower flow rate and maximum shower flow rate to the
list of issues for further research.

4.6
Item Ref 009: Update frequency and duration of use factors used in the Code Water
Calculator algorithms based on WRc CP337
BRE feedback

We agree with the principle that the most up to date use factors based on new homes need to be
incorporated into the Calculator in order to more closely reflect the impact that fittings wil  have on
water consumption.   We also recognise the limited data available from other sources to provide
such an update.

The issue related to the introduction of adjustments applied to individual use factors to take
account of inaccuracies in research is not a change that could be easily defended when justifying
changes made to the Calculator.  This change relates to the inaccuracies with the WRc use factors
where a 5% adjustment is made to take account for ‘lost days’ from the dataset.  There is
insufficient evidence or explanations given in Faber Maunsel ’s recommendations in order to justify
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such an adjustment and we do not feel this is a defendable position without further details and
research to demonstrate how this figure was established. We recognise that lost days may be
causing the use factors to overestimate consumption but until this can be properly quantified do
not recommend this can be incorporated at present.

Recommended action

Amend Calculator to reflect latest WRc CP337 report as included in the proposed algorithms.

Carry out further reviews of the WRc identiflow data to establish the impact of lost days on the
accuracy of use factors and identify potential adjustment factor.  This second action should be
added to the list of issues for further research.

4.7
Item Ref 010: Remove bidets from the Code Water Calculator
BRE feedback
From the review, the current method has been deemed as overestimating consumption when the
expert opinion is that bidet water consumption is negligible.  There is not a strong evidence base to
justify the level of water al ocated to the use of bidets and as such we suggest that due to this they
should be omitted from the calculation.
Recommended action
Remove Bidets from the Water Calculator.  We suggest that the consumption of water in bidets
could be an issue that is included in future microcomponent studies.  Whilst the inclusion of bidets
was appropriate at the time the Calculator was developed, the recent extensive expert review has
deemed that this is an overestimate and their consumption is in fact negligible.  It is also the case
that bidets are very rarely put in place in new homes and combined with the minimal water
consumption which general y is replacing the function of other fittings in the home, their removal
from the calculator is wel  justified.

4.8
Item Ref 012: Revise Code Water Calculator algorithms for basin and kitchen sink taps to
include a fixed proportion of water use
BRE feedback

Although including an issue which may make it harder to reach the targets may not seem logical
considering the Calculators current status, for fittings where there is generally a fixed use (kitchen
sinks) the Calculator gives no limit to savings, whereas it should be limited to the fixed volume use
typical of such fittings.  This is to ensure savings are not overestimated.

It is agreed that a fixed usage factor for wash hand basin taps is required and should be included.
Whilst the figure included for basin taps is not based on any specific research it is widely recognised
that basin tap usage does have a fixed proportion of use (e.g. for washing and shaving etc.).  The
figure assumed is a reasonable estimate (9% of basin taps usage per person per day) and not
including a fixed usage would allow an overestimate in the savings that can be achieved for taps
and make basin taps inconsistent with the way kitchen taps are assessed.  We recommend this
assumed level should be included in the revised calculator however making it clear that this is an
estimate and needs further research to improve this figures accuracy in the future.

14

Recommended action

Setting fixed usage levels based on Defra’s ‘Future Water’ publication into Water Calculator for
kitchen sinks is a good recommendation that should be actioned.  A fixed usage for basin taps
should be included at the moment as an estimate.   This should be improved at a later date when
further research is presented on the fixed usage from basins and sinks.

We recommend that the fixed proportion of usage applied to taps should be added to the list of
issues for further research.

4.9
Item Ref 013: Improve Code Technical Guidance on Calculator inputs for mixer taps,
separate hot and cold water taps and showers with multiple flow rates
BRE feedback

BRE recognises that the guidance in the technical guide could be improved to enhance technical
clarity and are aware of this issue based on Code assessor feedback.

Recommended action

Review the October 2008 tech guide to look for improvements that can feed into the new
Calculator document.

4.10
Item Ref 016: Revise the Code Water Calculator algorithm for rain and grey water systems
based on the new British Standards
BRE feedback

BRE agrees with this recommendation.  It is important that the Calculator is based on current best
practice.  The British Standard does however only cover rainwater and not greywater.  The
assessment method for greywater seems to be an area which has been omitted from this review.

Recommended action

Update CSH rainwater calculation in line with new BS8515 and require rainwater harvesting systems
to be designed in line with this new standard.  Further consideration needs to be given as to what
requirements are set in Part G for the design of rainwater systems however this is outside the scope
of this project.

A new British Standard for greywater is also due to be developed and we recommend that this is
included in the Code at a later stage when this has been formal y released.

4.11
Item Ref 021: Add waste disposal units in line with revised part G
BRE feedback

We understand that it is important to ensure all water consuming fittings are considered and to
bring the CSH and Part G into line. Waste disposal units wil  be added to the Calculator to address
this.

15

Recommended action

Add waste disposal units in line with calculation procedure set out in the recommendations.

4.12
Item Ref 022: Consider adding external water use to align Code Water Calculator results with
results for part G
BRE feedback

Our understanding of this recommendation is that this is to bring consistency between Part G and
the Code.  For the Code, external water use is included in the assessment of Wat 2 and it would not
be appropriate to include it in the assessment of Wat1 as this would impact on the targets which
are fixed at their current level. It does however make sense to include external water use in the
Calculator tables to indicate the consumption for Part G which can be a separate figure to that
indicated for the consumption calculated for the Code.  This needs to illustrate that this figure is an
additional inclusion for Part G and explain the reasons why this figure is not included in the Code.

Recommended action
Add a line to Calculator tables to indicate consumption for external water use, with a row to
calculate consumption for the Code (excluding external water use) and another row to indicate
consumption for Part G (including external water use).

4.13
Item Ref 025: Expand and improve Code Water technical guidance to improve good
plumbing design and specification

BRE feedback
It needs to be recognised that the Code is not a design guide; it is a standard for the assessment of
the sustainability of a home.  The inclusion of expanded technical guidance to improve plumbing
design and good specification would be an expansion on the Codes current scope and this would
also need to be expanded for other areas of the Code.

Recommended action
Review potential additional references to further design guidance such as British and European
standards that can be included in the Code technical guide.  This should just be limited to a list of
additional guidance and references rather than including the guidance within the technical guide.

4.14
Item Ref 011: Where fittings have varying specifications, use weighted averages in Water
Calculator algorithms for design flow rate of: multiple basin taps, multiple kitchen/utility
room taps, multiple showers and fill volume overflow for multiple baths.
BRE feedback

We understand the aims of this recommendation.   We are concerned that this recommendation is
not based on any specific research and there is a risk that the inclusion of this is not defendable.
We are also concerned that the impact of including such a method in a word format for part G
may cause an impact although the development of software to support this method would negate
this impact.  This issue is however important to address to reduce the potential for game playing
within the Calculator.  Game playing is where highly efficient fittings are put in place which may
not be acceptable to users in order to offset the consumption of a high water using fitting
16

elsewhere.  This can be done as the current calculator allows the consumption of fittings to be
averaged.  Providing a means of averaging does however al ow recognition for where a range of
fittings are to be provided.
Recommended action
BRE agrees that it is important to include this in the Calculator however suggest that the proposed
method is analysed further to look at:
•  the impact of including this measure in the updated Calculator
•  the potential for including this in a tabular format for Part G with testing carried out to assess
ease of use
We have put together an alternative methodology for addressing game playing and this is
explained below.  We recommend that this method is included in the updated Calculator as this
achieves the aim of the recommendation however with a more simplified approach.  Further
sensitivity testing of the Calculator to look at the impact of including this change is however
needed to look at potential impacts.
Proposed method
Where terminal fittings with varying flow rates and capacities are specified (e.g. hot and cold taps
with different flow rates, two types of showers etc.), the average consumption should be calculated
as set out below in the following Table 2:
a) Enter  the  full  flow  rate  or  volume  of  each  type  of  fitting  into  column  (a)  of  the  relevant
section of Table 2
b) For  taps,  where  there  are  separate  hot  and  cold  water  taps,  the  flow  rate  of  each  tap
should be entered separately as two tap types to calculate the average flow rate
c) Calculate the total consumption per fitting type
d) Calculate the average flow rate of the fitting types
e) Enter the flow rate of the fitting with the highest flow rate
f)  Calculate the weighted average by multiplying the maximum flow rate by a factor of 0.7

Where  the  average  flow  rate  or  capacity  is  lower  than  the  weighted  average,  the  weighted
average must be used as the flow rate or capacity to be entered into the Calculator.  This is so that
where  the  average  flow  rate  or  capacity  is  significantly  lower  than  the  maximum  flow  rate  or
capacity  specified,  the  calculation  limits  the  flow  rate  or  capacity  that  can  be  assumed.    The
factor  of  0.7  is  not  based  on  any  specific  research  and  is  just  a  factor  included  to  reduce  the
impact of game playing.  This figure is not fixed and where it is felt to not reduce game playing to
an adequate level, this may be adjusted further however this goes some way to address this issue.
Sensitivity testing is needed to look at this further.
Table 2: Example of averaging method: Basin Taps
Flow rate
Total per fitting type
Tap Fitting
Quantity (No.)
(litres/min)
(c)
Type
(b)
(a)
= (a) x (b)
1

2

3

4

Total   (d)

(Sum of all Quantities)
Total

(e)
(Sum of all totals per fitting type)
Average flow rate (litres/min)

(e) / (d)=
Maximum flow rate (litres/min)
(f)

Weighted average flow rate (litres/min)

[(f) x 0.7]=
17

Additional quick win suggested by BRE

4.15
Revise methodology for assessing white goods using a standardised capacity in Kg. (issue
not addressed by Faber Maunsell review)

Currently the Code uses the litres/use figure quoted on the energy label.  This is the litres per use for
the given capacity of the machine which may vary from 2-8kg for washing machines.  A smal er
machine would be used more frequently, a large machine less often but capacity is not taken
account of in the Code.

Recommended action

Scale the litres/use for washing machines and dishwashers to a standard capacity to ensure all
white goods are assessed on the same basis using the litres/kg for washing machines and
litres/place setting for dishwashers.  This should then be scaled up to the typical size of washing
machines and dishwashers to account for the typical daily usage of washing machines and
dishwashers per person per day.

5.  Potential actions needing further consideration
These recommendations are acknowledged as issues that should be included, yet at their current
status cannot at present be included, or are beyond the scope of a Code Water Calculator
review.  Some of the recommendations, BRE is not confident of the evidential basis for inclusion
however fol owing further work, may be included at a later date.  These issues do not ful y meet the
objectives set out in the report, but have the potential to meet the objectives with further work
carried out to investigate how the objectives can be made.

5.1
Item Ref 005: Establish a Code Water technical review mechanism
BRE feedback
The suggestion that a Code water technical review board could review situations where flexibility
to these limits can be al owed is questionable. We do not think that this recommendation should be
taken forward as establishing a group to question the validity of limits set out in a published British
Standard seems inappropriate.

Recommended action

We recommend that the flexibility to design limits should not be reviewed and that these should be
fixed.  We do however recommend that a code water technical review mechanism should be
maintained to ensure that any issues with the Calculator are reviewed on a regular basis.

5.2
Item Ref 007: Revise Calculator algorithms to include non-linear average flow intensities for
showers
BRE feedback
This issue has already been addressed elsewhere in the quick wins (see recommendation 4.5).
18

5.3
Item Ref 008: Ensure current and future Code Water Calculator revisions account for
microcomponent study methodology when adopting or deriving factors for use in
Calculator algorithms.
Item Ref 024: Undertake a scoping study to determine the relative impacts of
microcomponents of water use and saving measures not currently included in the
Calculator or addressed in the Code methodology. Use this as the basis for planning for the
expansion of the Calculator scope in future revisions.
Item Ref 026: Involve stakeholders in regular reviews of the Code Water Calculator
BRE feedback
These are issues for further consideration from CLG to inform future revisions of the Water Calculator,
Part G and the Code.
Recommended action
It is suggested that these issues are taken on board and that a paper is put together to set out what
future updates of the Code should consider.

5.4
Item Ref 014: Revise the Code Water Calculator algorithm for water softeners to include all
water uses supplied by the water softener and to derive regeneration frequency based on
daily demand for softened water
BRE feedback
The proposed algorithm is incorrect as this assumes the water softener regenerates every day, when
in fact this is variable as it depends on the water softener controls, litres of water consumed per day,
occupancy and hardness of the water.
It is agreed that the total water consumption of water softeners should be included however further
analysis is needed to review the impact of doing this to look at the potential impact on water
softener manufacturers.
Recommended action
1. Provide an additional calculation step to determine the number of regeneration cycles per day,
based on the total daily water consumption, occupancy and hardness of water.  This would only
apply to metered water softeners, some water softeners regenerate on a daily basis, so the daily
consumption makes no impact, as it wil  regenerate every day, no matter what the daily
consumption is.
This cannot yet be incorporated as a method of assessment needs further consideration to
determine the number of regenerations.  Further work is needed to look at a standard way of taking
into account of the hardness of the water.  This needs to be developed in liaison with
manufacturers so that a workable method can be developed.
2. Assess the impact of including the total water consumption of water softeners.  Where the
inclusions of a water softeners total water use makes it very difficult to comply with the water targets
using a range of acceptable fittings, it may not be appropriate to make this change in order to
minimise the impact on water softener manufacturers.  The current method does provide a
mechanism to encourage water softener manufacturers to increase water efficiency however so
this may not be a negative compromise.
19

5.5
Item Ref 017: Establish a water hierarchy to guide ongoing development of the Code
approach to water efficiency
BRE feedback
There is insufficient evidence to develop a water hierarchy and much further research is needed
looking at the merits of water saving devices such as low flow taps and showers verses using water
recycling technology.  By simply looking at this from the perspective of water efficiency the revised
Water Calculator can be used as it can indicate the proportions that each fitting contributes
towards daily water consumption.  Once issues such as impacts on energy, materials and waste
are brought in this gets much more complex and there is insufficient research in order to do this
such as life cycle assessments of each technology which would also need to consider replacement
intervals.  It may be that a different hierarchy would apply in each geographical region due to the
varying potential for rainwater harvesting which further complicates this issue.  Incorporating a
water hierarchy into the calculator would greatly extend the water calculators purpose and at
present it is simply to look at total household water consumption.  Water savings attributed to each
fitting are applied in the Calculator irrespective of the other environmental impacts such fittings
have.  Changing this would be a fundamental change to the calculator and consideration is
needed as to whether the Water calculator is the best medium for considering such issues and BRE
is of the opinion that it may not be.  This issue is further discussed in section 6.1.
Recommended action
A water hierarchy cannot be incorporated into the water calculator at this point in time.  This issue
is something that can be considered with a potential review of the role of grey and rainwater
however we do not see that this can be included at present until the research to establish such a
hierarchy is clear.

5.6
Item Ref 020: Limit all Calculator inputs and outputs to values rounded to the nearest 0.5
litres
BRE feedback
BRE agrees that the Calculator may be looking at this to a too greater level of detail however
suggest that the impact of such a change is assessed on completion of a revised Water Calculator
to ensure that this change does not have a net negative impact.
Recommended action
Set the calculated water consumption to one decimal place.  Review the impact of revising the
Water Calculator to the nearest 0.5, particularly for how it could be included in an excel based
tool.
5.7
Item Ref 023: Add an allowance for leakage to the Code Water Calculator and consider
including an equivalent saving for specification of leak detection and avoidance
BRE feedback
Although we understand the reasons for including this issue so that all areas of water consumption
in the home are taken account of.  We do not at the moment see a method for incorporating this
issue into the Water Calculator, or also see a way for measuring the benefit of leak detection
systems and prevention methods.  There also needs to be a package of measures developed that
could be incorporated into the Code in order to al ow the leakage factor to be reduced.  The
practicalities of such measures need to be further analysed such as the suitability of leak detection
20

measures on a domestic scale and the criteria that such measures would need to meet in order to
offset the leakage indicated in the Calculator.
The inclusion of leakage would also be another factor to make it harder to achieve the levels set
out in the Code and the factor of leakage may be al owed for when normalising the typical
consumption calculated by the Code to the measured data on typical UK consumption.
Recommended action
We suggest that further research is needed to determine the volume of water that is a result of
leakage from new households.  There also needs to be further research on the potential measures
that could be put in place in order to reduce this volume.
We do not support the inclusion of leakage just for the purposes of taking account of al  water uses,
where there is no means for this volume to be reduced through the promotion of leak avoidance
and detection measures and suggest this is considered further.

6. Issues put on hold
6.1
Item Ref 015: Review the role of rain and greywater systems in meeting Code Water levels
BRE feedback
BRE’s understanding of this recommendation is that it is to address questions on the lifecycle
impacts of rain and grey water and the need to consider efficient fittings before considering grey
and rainwater.
A possible route to achieving this proposed change is to consider whether rain and grey water
should only be considered where a minimum efficiency standard has been achieved.  This could
be set at 105 litres/person/day before rain and greywater can be considered, which effectively
means that grey and rainwater is only considered for levels 5 and 6 of the Code.  This change
would however be a diversion from the policy objectives set out in the development of the Water
Calculator and would remove flexibility that is currently allowed in the Code.  This may be seen as a
good thing in some ways for increasing sustainability to ensure that efficient fittings are provided first
before looking at the use of recycled water.  Some of the further considerations needed include:
•  The impact on published government policies such as the Governments Strategy for Water
set out in Defra’s ‘Future Water’ publication which clearly promotes the development and
use of grey and rainwater.  Changing the role of grey and rainwater in the Code would
contradict government policy.
•  Consideration of the replacement intervals when comparing water efficient fittings with
grey and rainwater systems
•  The geographical context of using rainwater
•  The impact on market transformation and the potential for slowing down the development
of innovative new grey/rainwater systems that may be addressing current criticisms of such
technology
•  The carbon cost of rain/greywater systems compared to the carbon savings from reduced
demand for mains water looking at a variety of systems and geographical regions
21

Before a conclusion can be made on what role rain and greywater should have in the Code, a
much more detailed review is needed to look at some of these issues, BRE are of the opinion that
there is insufficient justification for their exclusion from taking such a role in increasing water
efficiency or for a need to establish them in some form of water hierarchy at present.
The consideration of life cycle impacts is an issue which is only addressed in the Code in the
assessment of major building elements using the life cycle impact assessment technique set out in
BRE’s Green Guide to Specification.  To consider the lifecycle impacts of water fittings, the Code
would need to fol ow a consistent approach so that the lifecycle of other fittings required to meet
Code credit requirements are assessed in a consistent manner.  An appropriate lifecycle impact
assessment technique would also need to be developed and we would need to define the
considerations of such a technique such as whether this is an assessment of the product from
‘cradle to grave’ (extraction of materials and production to end of product life) or whether this is
just looking at the products impacts from ‘cradle to gate’ (extraction and production of materials).
It is not recommended by BRE that life cycle impacts is something that can yet be included in the
Code as this is a complex issue that would need further consideration.  Such a change to the code
would be fundamental and the impact of which would need further consideration.
Recommended action
Setting limits on flexibility for the use of rain and greywater would be a diversion away from
published Government policy and would remove an element of flexibility from the Code which
could potentially end up in reducing uptake of the Code for certain situations.  There needs to be a
clear justification for setting such limits and the case for this is not conclusive at the moment. We
suggest that a review is carried out to look at the role of rain and greywater in the Code.  Such
work should determine ways in which such technology could be encouraged to be more
sustainable and a set of criteria that could potentially be used to ensure that where such
technology is to be used, it meets certain sustainability and design requirements such as not having
an increased impact on carbon compared to using water efficient fittings.

6.2
Item Ref 018: Move to Calculator inputs based on measurement of best estimate of
site/system pressure
BRE feedback

BRE’s understanding of this recommendation is that it is to ensure flow rates indicated in the
Calculator are more reflective of the actual flow rates provided on site.  At the moment, flow rates
may be considerably higher or lower on site compared to the design flow rate.  This also helps push
developers towards considering site pressure to ensure more appropriate fittings are specified.

The concerns with requiring flow rates to be based on site pressure are that:
•  Manufacturers do not al  currently provide flow rates for a range of water pressure and so
this would make an impact on manufacturers needing to amend the testing methodogies
for their products and to amend their product information
•  There is no standard methodology that we are aware of in estimating site pressure and
there is a concern that site pressure may not be estimated on a consistent basis which
would bring inaccuracies in the assessment of this issue due to the complex nature of
carrying out such an estimate

Recommended action

We do support that it would be best to require the use of a best estimate of site pressure when
looking at flow rates, however, there needs to be further work carried out to determine a standard
methodology for estimating site pressure.  This includes:
22

•  Establishing what current methods there are for determining site pressure and where
possible include a recommended method that can be referred to
•  Carry out an analysis of the impact on manufacturers of requiring showers and taps to be
measured based on site pressure

6.3
Item Ref 019: Consider applying an occupancy factor to the Code Water Calculator figure
for household water demand
BRE feedback
Adding an occupancy factor would make consumption per person in homes with a lower
occupancy higher, and homes with a larger occupancy lower.  This would mean that homes with a
smal er occupancy have to provide more efficient fittings than homes with a larger occupancy.
Although it is general y understood that occupancy per person is higher in smal er homes, there is
not a clear set of research referred to, to show this relationship.
Recommended action
We recommend that a standard occupancy remains so that al  homes need similarly efficient
fittings.  To include occupancy, there needs to be a greater understanding of which fittings
consume more in smal  homes, rather than requiring an overal  greater efficiency requirement.   It is
questionable why it should be harder for homes with a smal er occupancy, when it may be
behavioural issues that will not be affected by more efficient fittings.
We recognise that smal er homes do general y consume more water per person than large homes
however there is no basis for this inclusion and the inclusion of this issue needs to be based on a
strong evidence base in order to justify smal er homes having to be designed as more efficient than
large homes.

6.4
Item Ref 027: Review higher target levels of the Code and relative spacings of the targets
along with the range of water efficiency options currently available to meet each target
level
BRE feedback
To ensure appropriate targets are set for each level of the code with appropriate fittings for each
level.
Review the fittings required to meet the Code Water targets based on the revised algorithm.  Assess
whether the type of fittings required to meet the various levels are appropriate.
Recommended action
It is not possible to address the targets set out in the Code at the moment as these are fixed. It is
however sensible to review the type of fittings that would be needed to meet this level.
This recommendation is highly dependent on a review of the role of grey and rainwater.  The results
of such a review would need to feed into a potential review of the upper levels of the Code. It
would also be appropriated to look at alternative approaches that could be included to reduce
water consumption such as leakage rates and other opportunities for saving water that were
identified such as long draw-offs.  All such issues cannot yet be incorporates into the Calculator as
the relative savings cannot yet be quantified due to a lack of available data.  This is a
23

consideration to be looked at as part of the research needed to look at future reviews of the Water
Calculator.
7.  Example specifications
Typical Consumption: Normalising the Water Calculator
The fol owing illustrates the revised Water Calculator using typical UK fittings as defined in Faber
Maunsel s review.  A normalisation factor of 0.91 has been derived from this to amend the
calculation so that the consumption indicated by the Calculator using typical UK fittings correlates
with the typical UK consumption of 150 litres/person/day.
The various use factors (duration, frequency and percentage of use) have been merged into one
use factor.  This is to reduce the number of steps required to carry out the calculation.  An
explanation of how each use factor is derived is explained below.

Table 3: The Water Calculator for New Homes
Installation
Unit of
Capacity /
Use
Fixed
Litres /
Type
measure
flow rate
factor
use
person /
(litres)

(litres)
day

(1)
(2)
(3)
= (1) x (2)
+ (3)
WC (single
Flush volume
6
4.42
0.00
26.52
flush)
WC (dual
Full flush

1.46
0.00

flush)
volume
Part Flush

2.96
0.00

volume
Taps (other
Flow rate
9
1.58
1.58
15.8
than kitchen or  (litres/minute)
external taps)
Bath
Capacity to
225
0.11
0.00
24.75
overflow
Shower
Flow rate
12
4.37
0.00
52.44
(litres/minute)
Kitchen sink
Flow rate
12
0.44
10.36
15.64
taps
(litres/minute)
Washing
Litres/place
9.66
2.1
0.00
20.3
Machine
setting
Dishwasher
Litres/place
1.25
3.6
0.00
4.5
setting
Waste
Litres/use
If present = 1
3.08
0.00
0
disposal unit
Water Softener

0
24

  Calculated use
159.95
(litres/person/day)
Total Consumption (Part G)
Calculated
Normalisation  External
Total
Use
factor
Water Use
consumption

(litres) 1

(2)
(3)
= [ (1) x (2) ] + (3)
(1)
160.65
0.91
5.0
150.6
Total Consumption (Code for Sustainable Homes, Issue Wat1)
Calculated
Normalisation  Contribution
Total
Use
factor
from
consumption

recycled

water 2
= [ (1) x (2) ] - (3)
(1)
(2)
(3)
159.95
0.91
0
145.6

8.  Use factors
Use factors
The overall use factors used in the Water Calculator are derived as follows:
(1) x (2) + (3) = overal  use factor
Table 4: Illustration of how the use factors have been calculated
Installation
Quantity /
Flow rate
Uses per
Overall
Type
duration of
modification
day
use
use Factor
factor
factor
factor

(1)
(2)
(3)
(4)
WC (single
1.0
1.0
4.42
4.42
flush)
WC (dual
0.33
1.0
4.42
1.46
flush)
0.67
1.0
4.42
2.96
Taps (other
0.43
0.39
9.42
1.58
than kitchen or
external taps)
Bath
1.0
0.50
0.22
0.11
Shower
5.6
1.0
0.78
4.37
Kitchen sink
0.43
0.29
3.56
0.44
taps
Washing
6.0
1.0
0.35
2.1
Machine
Dishwasher
12.0
1.0
0.30
3.6
25

Waste
2.46
1.0
1.25
3.08

disposal unit

9.  Examples of compliant specifications
Best new specification
The fol owing illustrates the consumption achieved using the new Calculator with the use of the
best available water fitting specification.  The fittings used are those that do not go below minimum
levels of user acceptability.  This is also using the default figures for white goods (49 litre washing
machine and 15 litre dishwasher) to reflect the best new specification applicable to social housing,
where white goods are rarely provided.

Table 5: Illustration of consumption with Best New Specification
Installation
Unit of
Capacity /
Use
Fixed
Litres /
Type
measure
flow rate
factor
use
person /
(litres)
day
(litres)
WC (single
Flush volume

4.42
0.00

flush)
WC (dual
Full flush
4.5
1.46
0.00
6.57
flush)
volume
Part Flush
2.5
2.96
0.00
7.40
volume
Taps (other
Flow rate
4
1.58
1.58
7.90
than kitchen or  (litres/minute)
external taps)
Bath
Capacity to
165
0.11
0.00
18.15
overflow
Shower
Flow rate
6
4.37
0.00
26.22
(litres/minute)
Kitchen sink
Flow rate
6
0.44
10.36
13.00
taps
(litres/minute)
Washing
Litres/kg
8.17
2.1
0.00
17.16
Machine
Dishwasher
Litres/place
1.25
3.6
0.00
4.5
setting
Waste
Litres/use
If present = 1
3.08
0.00
0
disposal unit
Water Softener

1.00
0.00
0

  Calculated use
100.9
(litres/person/day)
26

Total Consumption (Part G)
Calculated
Normalisation  External
Total
Use
factor
Water Use
consumption

(litres) 1

(2)
(3)
= [ (1) x (2) ] + (3)
(1)
100.9
0.91
5.0
96.8

Total Consumption (Code for Sustainable Homes, Issue Wat1)
Calculated
Normalisation  Contribution
Total
Use
factor
from
consumption

recycled

water 2
= [ (1) x (2) ] - (3)
(1)
(2)
(3)
100.9
0.91
0
91.8

Best new fittings (beyond levels of user acceptability)
The fol owing table is a specification of fittings beyond the levels of user acceptability.  The fittings
used are fittings that from BRE Globals experience are currently being used for a number of Code
assessments at present to achieve Code level 3.  This specification achieves 69 litres/person/day
under the revised Calculator which is equivalent to Code level 6 however without the use of grey or
rainwater.  Due to the fact that fittings are used that go beyond minimum levels of user
acceptability, it is unlikely that such a low water consumption would be achieved in practice as the
duration of use taken account for in the Calculator is likely to be underestimated.  The low flow
rates are likely to mean that users have to use the fittings such as showers and taps for longer
periods of time in order to fulfil the desired function.  Occupants are also likely to replace the fittings
with much less efficient fittings if they aren’t working.  Arguably grey or rainwater could be a much
better solution to achieving this level, as at least acceptable fittings could be used and offset by
rain or greywater to meet this level of efficiency.
The fact that you can achieve level 6 with the use of inappropriate fittings illustrates the importance
of setting minimum acceptable flow rates, otherwise, with the updated Calculator, it may be
possible to reach code level 6 by using fittings not acceptable to users and this route is very likely to
be taken if not only to achieve the tradable credits available at level 6.
The fact that you can achieve level 6 with a specification currently used to achieve level 3 is also a
serious concern.  Developers that have achieved level 3 will not be happy that they could now
achieve level 6 for Wat 1 with the same specification.  There is also the potential for negative press
due to the fact that level 6 can be achieved with fittings that are not appropriate (e.g. 2 litre taps).
These impacts could be negated with the use of recommended minimum flow rates and
capacities for terminal fittings. Whilst these are only recommended, they would emphasise the fact
that even if theoretical y level 6 can be achieved with unacceptable fittings, it is acknowledged
that the fittings are not appropriate.  Keeping them as recommended rather than mandatory
would reduce impacts on manufacturers of fittings that fal  below these minimum levels.
Instal ing fittings that are below minimum levels is of course the developers choice and the impact
of providing fittings which do not meet the needs of occupants may make it harder to sell homes,
or cause problems with warranties.   These are impacts that developers should consider.
27

The fol owing table illustrates the use of fittings below user acceptability limits and the water
consumption that can be achieved.
Table 6: Illustration of consumption using fittings that go beyond user
satisfaction
Installation
Unit of
Capacity /
Use
Fixed
Litres /
Type
measure
flow rate
factor
use
person /
(litres)
day
(litres)
WC (single
Flush volume

4.42
0.00

flush)
WC (dual
Full flush
4.0
1.46
0.00
5.84
flush)
volume
Part Flush
2.7
2.96
0.00
7.99
volume
Taps (other
Flow rate
2
1.58
1.58
4.74
than kitchen or  (litres/minute)
external taps)
Bath
Capacity to
105
0.11
0.00
11.55
overflow
Shower
Flow rate
4
4.37
0.00
17.48
(litres/minute)
Kitchen sink
Flow rate
2
0.44
10.36
11.24
taps
(litres/minute)
Washing
Litres/use at
40
0.35
0.00
14.00
Machine
6kg load
Dishwasher
Litres/use at
10
0.30
0.00
3.00
12 place
settings
Waste
Litres/use
If present = 1
3.08
0.00
0
disposal unit
Water Softener

0

  Calculated use
75.8
(litres/person/day)

Total Consumption (Part G)
Calculated
Normalisation  External
Total
Use
factor
Water Use
consumption

(litres) 1

(2)
(3)
= [ (1) x (2) ] + (3)
(1)
75.8
0.91
5.0
74.0

28

Total Consumption (Code for Sustainable Homes, Issue Wat1)
Calculated
Normalisation  Contribution
Total
Use
factor
from
consumption

recycled

water 2
= [ (1) x (2) ] - (3)
(1)
(2)
(3)
75.8
0.91
0
69.0

Part G compliant example
Table 7: Illustration of fittings required for Part G compliance
Installation
Unit of
Capacity /
Use
Fixed
Litres /
Type
measure
flow rate
factor
use
person /
(litres)
day
(litres)
WC (single
Flush volume

4.42
0.00

flush)
WC (dual
Full flush
6.0
1.46
0.00
8.76
flush)
volume
Part Flush
4.0
2.96
0.00
11.84
volume
Taps (other
Flow rate
6
1.58
1.58
11.06
than kitchen or  (litres/minute)
external taps)
Bath
Capacity to
180
0.11
0.00
19.80
overflow
Shower
Flow rate
8
4.37
0.00
34.96
(litres/minute)
Kitchen sink
Flow rate
8
0.44
10.36
13.88
taps
(litres/minute)
Washing
Litres/kg
10
2.1
0.00
21.00
Machine
Dishwasher
Litres/place
1.08
3.6
0.00
3.90
setting
Waste
Litres/use
0
3.08
0.00
0
disposal unit
Water Softener

  Calculated use
125.2
(litres/person/day)

29

disposal unit
Water Softener

  Calculated use
109.5
(litres/person/day)

Total Consumption (Part G)
Calculated
Normalisation  External
Total
Use
factor
Water Use
consumption

(litres) 1

(2)
(3)
= [ (1) x (2) ] + (3)
(1)
109.5
0.91
5.0
104.7

Total Consumption (Code for Sustainable Homes, Issue Wat1)
Calculated
Normalisation  Contribution
Total
Use
factor
from
consumption

recycled

water 2
= [ (1) x (2) ] - (3)
(1)
(2)
(3)
109.5
0.91
0
99.6

31