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Part G Water Calculations

Do you need to provide water calculations for Code for Sustainable Homes or Building Regs?

Build Energy can provide quick, easy and bespoke reporting to get you through – whether you need Part G water calculations or the equivalent Code for Sustainable Homes reporting.

Why Do You Need Part G Water Calculations?

Building regulations demand that new builds meet the minimum 125L litre per-person-per-day limit.

If the development is subject to the Code for Sustainable Homes, you will also be required to reduce internal potable water use further through the Wat 1 category.

Each Code level sets a mandatory limit on internal water consumption – this is demonstrated by producing calculations, based on occupancy, fittings and flow rates within the water efficiency calculator.


The current limits are set as follows:

  • Level 1 & 2 – Less than or equal 120L p/day
  • Levels 3 & 4 – Less than or equal 105L p/day
  • Levels 5 & 6 – Less than or equal 80L p/day

There are also credits available for meeting these targets.

A number of measures can be taken to reduce indoor water use. Flow restrictors are a convenient means to retrofit existing fittings. Low flow shower heads, low flush wc’s or even smaller baths may be fitted.

Efficient appliances, grey water and rainwater recycling can also be specified.

We can suggest solutions and products which are efficient, practical and cost effective.

The Water Efficiency Calculator for New Dwellings

Our bespoke Part G water calculations are based on “The Water Efficiency Calculator for New Dwellings” – The Governments national calculation methodology.

This provides clear, concise information for both you and Building Control – meaning that you get signed off quickly and easily. We will receive:

  • Notice of Water Efficiency (as required by 37(1)
  • Summary page together with all corresponding completed tables
  • Separate “Design” (including Builders check list) and “As Built” Reports
  • Code For Sustainable Homes rating against Wat 1

Need help with Part G Water Calculations?

Just call us on [xyz-ihs snippet=”Dorset-Phone-Number”] or send us your enquiry

Recent Projects

"BE are fantastic building energy assessors, with competency across many areas. We have found them very useful on small and large projects. With the larger projects they can provide a range of assessments with one point of contact. We submitted a planning application for 224 residential apartments for a site in Luton. BE provided the flood, acoustic, heat loss and SUDS reports. The scheme was consented and reports were excellent. We have found them to been frank and honest with their advice. They are also lovely people to work with… which is very important."

Adam Covell
- ECA Architecture

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