Water usage calculations are required as part of the new construction process for building control sign off (Part G of the Building Regulations), nowadays you must achieve a projected water consumption of less than 125 litres per person per day.bathroom basin with tap running

This calculation must be in accordance with the process set out in the Water Efficiency Calculator for new dwellings.

We can provide these calculations for you as required to comply with the Approved Document G, to help with this we can often advise on the acceptable efficiency for each fitting.

What affects the projected water consumption of a dwelling?

Factors that affect the calculated water consumption of a dwelling include:

  • The flow rate of showers and taps;
  • The capacity of baths;
  • The flushing capacity of WCs;
  • The consumption per place setting of dishwashers;
  • The consumption per kilogram of dry load for washing machines;
  • The efficiency of water softeners (where present); and
  • Whether there is any on-site rainwater or greywater harvesting.

What happens should you fail the calculations?

  • If you have not purchased or installed the goods yet, then we can advise on suitable units that will help to pass.
  • If the property has been fitted out, there are still some options to meet the requirements and ensure compliance.