Part G Water Calculations

Building Regulations require that new dwellings meet the minimum 125 litres per-person-per-day of potable (safe to drink) water.

If the development is subject to a planning condition, you may also be required to reduce internal potable water use further, often to 105 litres; this is at the discretion of the local authority.


What are Part G Water Calculations?

Since 2010, Approved Document G – Sanitation, hot water safety and water efficiency, has required that all construction projects, whether that be an extension, conversion or new build, are water efficient enough to supply this 125 litre per person minimum threshold.

Part G water calculations take into account:

  • Taps
  • Toilets
  • Baths
  • Showers
  • Other water producing appliances including dishwashers and washing machines


The Water Efficiency Calculator for New Dwellings

This is the Government’s national calculation methodology which provides clear, concise information for both you and Building Control.

As well as providing the required Notice of Water Efficiency in 37(1), Cook Brown can also provide you with:

  • Summary page with all completed tables
  • Design calculations to help you specify the fitting efficiencies
  • As Built calculations for sign off
  • Enhanced As Built report, with optional site visit and photographic evidence submission


How Much do the Part G Calculations Cost?

Whether you need the calculations for a planning condition or building control sign off, our prices start from just £65 per calculation, and we can offer discounts for multiple dwellings. Get in touch today for a bespoke quote to suit your needs.

Get a quote today >


How Can You Improve Your Water Efficiency?

Water use is demonstrated by producing calculations based on occupancy, fittings, and flow rates. Several measures can be taken to reduce indoor water use including:

  • Flow Restrictors
  • Low flow shower heads
  • Low flush WCs
  • Efficient washing machines
  • Upgraded dishwashers

We can provide you with various solutions and products that can be installed into your home or project to provide efficient, practical, and cost-effective water supply.


Part G Water Calculations with Cook Brown Energy

Get started with your water calculations today, with Cook Brown’s technical team.

To produce the report, we will need additional information regarding the number and type of water outlets in the proposed dwelling.

For more guidance and a bespoke quote for your need get in touch with our technical team on 01275 846995 or email