How to get it right: Domestic water usage for new dwellings

The building regulations specify limits on water use for newly constructed homes and those formed by converting existing buildings. Water usage from WCs, wash basins, sinks, showers, baths, and white goods such as dishwashers and washing machines are all included in the requirement.

English regulations

In England, the regulations require that the average water usage be no more than 125 litres per person per day unless the planning permission for the home has specified that this needs to be reduced to 110 litres per person per day. The planning permission will state whether this standard has been applied. It's important that the person submitting the building regulation application informs the local authority building control department of this planning requirement.

Estimated water usage needs to be calculated unless the water fittings used follow the guidance in tables 2.1 and 2.2 of Approved Document G (England).

Table 2.1: Water fittings route for 125 litres per person per day standard.

 Table 2.2: Water fittings route for 110 litres per person per day standard.

Where the water fittings to be used exceed the consumption stated in the tables or where a shower is not to be provided or where a waste disposal unit, water softener or water re-use is proposed the estimated water usage should be calculated using the method contained in Appendix A of Approved Document G. 

Visit here for further information for providing water calculations 

Welsh regulations

In Wales, the regulations require that the average water usage be no more than 110 litres per person per day for new dwellings and 125 litres per person per day for dwellings formed by conversion of an existing building.

The estimated water usage needs to be calculated unless the water fittings used follow one of the performance standards in table 2.1 of Approved Document G (Wales). 

Where the water fittings to be used exceed the consumption stated in the tables or where a shower is not to be provided or where a waste disposal unit, water softener or water re-use is proposed the estimated water usage should be calculated using the method contained in Annex 2 of Approved Document G.

What your building control team will need to see

Building control in both countries should be provided with water efficiency calculations at the design stage where a fittings approach is not followed. Any changes to the fitting’s specification should be included in an updated calculation and resubmitted.

Your local authority building control authority will need to be issued with a notice within five days of completion of the home stating the potential water consumption. They should also be provided with a final version of the water efficiency calculation at the same time.

Further information

Please contact your local building control team with any queries - you can find their direct contact details using the postcode search at the top of this page.

Please Note: Every care was taken to ensure the information was correct at the time of publication. Any written guidance provided does not replace the user’s professional judgement. It is the responsibility of the dutyholder or person carrying out the work to ensure compliance with relevant building regulations or applicable technical standards.