How Part G expresses the water-use limit for a new home and why fittings choice drives the result.
Part G controls how much water a new home is expected to use. The requirement is written as a limit on litres per person per day, calculated from the fittings that are installed rather than measured once people move in.
The normal new-dwelling limit is 125 litres per person per day. Where a tighter, optional requirement applies (for example because a planning condition calls for it), the limit is 110 litres per person per day.
The calculation adds up the assumed use of each type of fitting: taps, showers, baths, WCs, washing machines and dishwashers. Because the result depends on the fittings, the practical way to pass is to specify efficient ones.
That means lower-flow taps and showers, dual-flush or low-volume WCs, and appropriately sized baths, all chosen so the totalled figure stays under the limit.
For revision, remember two things: the limit is per person per day, and it is driven by fittings selection. The exact numbers and the calculation method are set out in the current Part G, so confirm them there.
This is a design-stage requirement, so it sits alongside, not instead of, the day-to-day water-fittings rules that keep water wholesome.