This programme investigates the anticipated new Approved Document G on Sanitation, hot water efficiency and water efficiency, as well as the Water Efficiency Calculator, both of which are devised to monitor the amount of water used in a typical dwelling house.

The Building Regulations (England and Wales) Approved Document G, scheduled for publication in 2010, is compared to the previous 1992 edition, while regulation 17K and its performance target of 125 litres per person per day is explained in the context of Code for Sustainable Homes levels. The document's stipulations on water quality are discussed, including definitions of 'wholesome' and 'non-wholesome' water, and there is a detailed look at hot water safety. The Water Efficiency Calculator is explored as a tool for assessing the notional water efficiency of new dwellings. The mathematical workings of the Water Calculator are explained and an example calculation worked through.