Water Efficiency Calculations (Part G)

Water Efficiency Calculations are required to comply with Approved Document G and the Code for Sustainable Homes.

Please watch our services video

Water Efficiency Calculations are now required for Building Control purposes (Approved Document G), and planning purposes (Code for Sustainable Homes). The purpose of water efficiency calculations is to establish the whole house portable water consumption in new dwellings. This is also applicable to conversion schemes.

On April 6, 2010, Part G included the need for water efficiency calculations to be carried out for new dwellings and conversions. The permitted usage is 125 litres of water per person per day. This includes internal water and external use.

This breaks down as internal water use of 120 litres per person per day, in line with Code levels 1 and 2, plus an allowance of 5 litres per person per day for outdoor use.

This will be specified by RTS using the methods set out in the ‘Water Efficiency Calculator for New Dwellings’ also used for the Code for Sustainable Homes.

Introduced in 2007, the Code for Sustainable Homes is the government’s main tool for improving the environmental specification of new homes. Points are awarded for achieving standards in 9 different aspects of development. There are 7 levels of specification ranging from level 0 (the Building Regulations) to level 6 (zero carbon). Water consumption inside the home is one of the compulsory aspects to address to achieve minimum standards at level 1-6 of the code. A total of 5 credits are available for water consumption.

Design and As-Built water efficiency calculations need to be provided. The water consumption specification for increasing Code levels are:-

Performance Target                       Max  (Litres/ person/ day)

17.k compliance                                          125

Code for Sustaianable Homes (Level 1/2)         120

Code for Sustaianable Homes (Level 3/4)         105

Code for Sustaianable Homes (Level 5/6)          80

Please contact us if you have any questions regarding water efficiency calculations.