All new residential properties – whether newly built or converted – must now meet specific water efficiency targets by law. Under Part G of the Building Regulations, a maximum water usage figure of 125L per person per day must be achieved. As of 1st October 2010, non-compliance may adversely affect a dwelling’s SAP rating, and therefore its EPC rating.

The calculation must be submitted at both the design and as built stage and is required to show the potential consumption of wholesome water per person per day. The calculation is based on fixtures and fittings in a dwelling and also any greywater or rainwater harvesting technologies.