What is a Water Efficiency Calculation?
A water efficiency calculation is a legal requirement set out in Part G of the building regulations. These calculations are required for all new build dwellings, as well as conversions. 
Part G requires that a dwelling must not use more than 125 litres per person per day. However, some planning authorities may enforce stricter targets, such as 110 litres per person per day. Stricter targets are often implemented by London planning authorities where compliance with the London Plan is required.  If you are unsure of your target, we will check this for you.