Part G Water Efficiency Calculations

Part G Water Efficiency Calculations

Part G of the Building Regulations limits how much water a new home is designed to use. Building control needs a calculation for every new dwelling before completion. We produce it from your fittings schedule and tell you which fittings to change if it does not meet the target.

The targets

• 125 litres per person per day. The standard for all new homes in England.
• 110 litres per person per day. The tighter optional standard, which applies where a planning condition asks for it. The London Plan and many councils in water-stressed areas require 110.

Check your planning decision notice. If there is a water condition, it says which figure applies.

How we calculate it

We use the government's water efficiency calculator. It takes the flow rates of taps and showers, the flush volumes of WCs, the bath capacity, and the water use of the washing machine and dishwasher.

What we need from you

• The sanitaryware and appliance schedule, with make and model or the flow rates and volumes
• The number of each fitting in each home
• The planning condition, if there is one

Changes coming

The government has consulted on a lower limit for new homes. At October 2026 no change has been confirmed. We apply the figure in force for your project.

Questions we get asked

When should I order it?
Before you buy the sanitaryware. If the fittings are already on site and the calculation does not pass, changing them costs far more.

Does it apply to conversions?
Yes, where the work creates a new home. It does not apply to extensions.

Send us your fittings schedule by email or WhatsApp and we will come back with a quote and a turnaround time.