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Water Efficiency Calculator

Water efficiency calculations are required to meet the Government regulations for new build dwellings or flats, and most dwellings or flats newly formed as a result of a change of use or conversion of an existing building. For such newly formed  dwellings/flats in Cornwall the default legal requirement is a design water efficiency of 125 litres/person/day at the time of writing. (Newly formed dwellings elsewhere in the country where water shortages often occur may be subject to the higher efficiency requirement of 110 litres/person/day which is called the ‘optional requirement’ in Approved Document G.) Some home owners or developers may also want to try to achieve a higher water efficiency for their own reasons (e.g. lower water bills or for environmental reasons) so make sure to check what the designer and client have specified as it may be more onerous than the default 125 litres/person/day required in Cornwall by Building Regulations.

If you are building a new home and are not adopting a ‘fittings’ based approach detailed in section G2 of Approved Document G, you will need to calculate the water consumption of the dwelling.

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The calculation must be carried out in accordance with the methodology contained in Appendix A of Approved Document G and can be completed using the Water Efficiency Calculator tool.

As it is unlikely that sufficient information is available regarding flow rates etc for the relevant appliances at the time the building regulation application is deposited, we are happy to make the provision of the calculation, prior to the fittings / appliances being installed on site, a condition of approval. 

It is essential that the relevant site personnel are aware that the calculation is required as we are unable to issue a completion certificate without a calculation showing compliance with the Regulations having been received.