Wat 01 - Water consumption - BREEAM Knowledge Base

Alternative calculation method - KBCN0547

Where it is not possible to use the standard approach to determine the building’s total water consumption, the assessment can be completed on an elemental basis. This applies even in cases where the Wat 01 Excel calculator tool has a section for a broader building type, but the defined activity areas do not match the specific project under assessment. For example, although Wat 01 calculator includes a retail calculator, bars and restaurants should be assessed using the alternative calculation method, as no relevant data is available for the specific activity within retail. Where the activity areas of the building under assessment do not allow using the relevant building type’s calculator, then the alternative calculation approach should be used.

BREEAM New Construction UK 2018 – Post-Occupancy Stage assessment - KBCN1532

Following the publication of UK NC V6 it was announced that the Post-Occupancy Stage (POS) assessment within BREEAM will close with immediate effect. While we will no longer be offering this as an assessment option, the essence and intent behind the criteria will remain. At this stage, we will not be re-issuing the UKNC 2018 manual. Therefore, reference to POS will remain within the following issues:

Ene 01 Reduction of energy use and carbon emissions (two credits for Post-Occupancy Stage)
Ene 02 Energy monitoring
Wat 01 Water consumption
Wat 02 Water monitoring

To award the relevant credits, the references to ‘Post-Occupancy Stage assessment’ should be read as ‘Post-Occupancy Evaluation’ and carried out with the same intent; to understand and close the performance gap. For assessments that have been certified at Post-Construction, are in progress or are new assessments, the Post Occupancy Evaluation process should continue to be followed, however there is no formal post-occupancy BREEAM certification stage. Rating systems such as BREEAM in-Use and NABERS UK Energy for Offices are examples of tools that can be used to measure performance in the operational phase.

18-05-23: KBCN edited to illustrate that credits can be awarded.

Commercial dishwasher appropriate data - KBCN0687

If the component is present in the building but the appropriate data is unavailable from the manufacturer's product information i.e. uses a different unit of measurement, then the baseline performance level for the specified component should be used in the WAT 01 calculator. BRE Global is unable to provide a calculation method to convert data in to the correct unit for the WAT 01 calculator tool.

Flow rate for a mixture of taps - KBCN0173

Whichever is the higher of the 'average flow rate' or the 'proportionate flow rate' should be used within the Wat 01 Calculator.

Flow restrictors - KBCN0976

If a flow restrictor can be demonstrated to effectively reduce the flow of water and it is integral to the fitting or supply pipework (ie not easily removed by the building occupant), this can be accounted for in calculations for this Issue. Such devices must be fit-for-purpose. Proprietary flow restrictors, therefore partly-closed isolation valves, for example, are not an acceptable solution.

Flushing control – patients with frail or infirm hands - KBCN0414

When determining whether the WC fittings in healthcare facilities are suitable 'for operation by patients with frail or infirm hands', the assessor should be satisfied that this requirement has been met, as it will be product type dependent. If unclear to the assessor, evidence obtained from the relevant manufacturer confirming that their product is specifically designed, and has been tested and approved, for this purpose would be acceptable.

16/04/2018 Rewritten for clarity

Measuring the flow rate of domestic components - KBCN0641

On site testing can be carried out by an appropriate professional to determine the flow rate and capacity of domestic components. This must be overseen by the client’s facilities manager and as-built drawings must be provided to confirm the presence and location of the components and any flow restrictors. Note that the conditions under which the testing is completed must be recorded, e.g. the pressure and the temperature of the water for taps. The assessor could conduct the test provided they are able to carry it out accurately.

15/02/2021: amended to cover all component types.

Process water to offset potable water demand - KBCN0586

Where it is demonstrated that it is safe to do so, process water resulting from the building under assessment, can be considered for off-setting potable water demand from components that would otherwise be supplied using potable water, when in line with the criteria requirements for greywater systems. Process water resulting from the building under assessment can be considered as a form of greywater for the purposes of off-setting potable water demand.

21 Dec 2021 Additional wording added, requiring it to be demonstrated that process water is safe to use and KBCN applied to BIU standards.

Rainwater harvesting standard – BS 8515:2009 replacement - KBCN1179

BS 8515:2009 (+A1:2013 where relevant) has been withdrawn and replaced by BS EN 16941-1:2018, which can be used for new assessments. The basic approach in BS EN 16941 is equivalent to the intermediate approach in BS 8515 is. The detailed approach is still described in the same way.

The relevant schemes will be updated in the next reissues.
03.11.2021 Issue 2.0 of the UK RFO technical manual amended.

Sanitary fittings used in religious practices – updated - KBCN1624

Such fittings should not be included in the scope of this Issue. Please refer also to KBCN0418 This guidance relates to fittings and facilities used in some religious practices, for example, for washing before prayer.

03 Nov 2023 - Updated. Previous guidance was incorrect and contradicted the approach outlined in KBCN0418

Shower with multiple shower heads - KBCN0855

To calculate the water use of a shower with more than one shower head, one of the following should be done:

If all of the shower heads can be turned on at once, the flow rates should be added up.
If the shower heads can only be used one at a time, the highest flow rate should be used

22 Feb 2024 - Applied to BIU, BREEAM NC and RFO standards

Specialist assisted baths in care homes - KBCN0228

Specialist assisted baths in care homes or similar specialist applications can be excluded from the assessment of this issue. Due to the specific access and care needs of users, it may not be possible to reduce the volume of specialist assisted baths.

Urinals – calculation of litres/bowl/hour - KBCN1010

A flushing frequency of two flushes per hour is used in the Wat 01 tool and should be applied when calculating the volume of water dispensed by urinals and compared against the water efficient consumption levels by component type for the Wat 01 issue. This method should be applied to calculate litres/bowl/hour. For example, a 13.5 L cistern feeding 3 bowls which is flushed 2 times per hour: (13.5 L / 3 bowls) x 2 times an hour = 9 litres/bowl/h.

Using water from natural underground sources to offset water consumption - KBCN00094

Water from natural underground sources (for instance aquifer water accessed via boreholes) cannot be used to offset:

NC / RFO: potable water consumption.
IU: utility supplied water consumption.

A significant amount of water used for public consumption is already drawn from aquifers. Private boreholes may be drawing water from the same sources as public utility companies.

27-Mar-2024 - Title and text updated to broaden definition. Scheme applicability updated.

Washer dryers - KBCN0699

Where a washer dryer is specified, the water consumption figure for the wash and dry cycle should be used. The drying cycle of a washer dryer is taken into account because it usually uses water during this drying process (e.g. for cooling during the drying cycle) and in some cases, this water usage can be significant.

18-Nov-2022 - Updated to apply to BREEAM In-Use Version 6

Washing machines and dishwashers – Water consumption data - KBCN1571

The water consumption data used to demonstrate compliance may be based on the lowest full wash cycle (i.e. not a pre-wash cycle, for example).

Water consumption calculation for sensor taps - KBCN0180

The water flow rate of sensor taps can be entered directly into the flow rate cells of the Wat 01 tool. The amount of water dispensed by sensor taps for each use is determined by occupant demand in the same way as normal taps. Therefore, the default frequency of use will be applied in the Wat 01 tool and no adjustment calculation is needed for sensor taps.

Water fittings specification evidence at design stage - KBCN0420

For a design stage assessment, it is acceptable to provide data based on reasonable assumptions if the final specification of fittings is not yet available.

Water fittings used for a process related function - KBCN0418

Water fittings used for a process related function, e.g. low level ablution taps, laboratory / classroom taps, scrub-up taps, cleaners' sinks etc., should be excluded from the assessment of regulated water consumption. Only kitchen taps and those used for general hygiene washing are to be included in the assessment of regulated water consumption.

04/08/17 Added low level ablution taps (typically used for religious purposes) to exemptions.

New Construction / UK / 2018 / 05 Water /

Wat 01 - Water consumption