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About part-g.co.uk

part-g.co.uk is a free water efficiency calculator for new dwellings in England, for designers, builders, developers and self-builders who need to show Part G compliance.

Who's behind it

I'm Andrew Chambi, an energy consultant based in London with nine years' experience in energy and compliance work on homes and commercial buildings. I hold OCDEA accreditation with Elmhurst and I'm a CIBSE Low Carbon Consultant and Low Carbon Energy Assessor. More about my experience and how to check my credentials.

I built the calculator because the same questions come up again and again, and the honest answers are buried in government documents. part-g.co.uk is a personal project, separate from my day job.

Why it exists

Most Part G calculators tell you whether a specification passes. They don't tell you what to change when it fails, or how much room you have when it passes. This calculator does both, so you can settle the bathroom spec before it's ordered, not after building control queries it.

Other Building Regulations tools

For the Part O overheating simplified method and the Future Homes Standard transitional rules, see the free checkers on buildingregs-hub.co.uk, built and checked the same way.

How the numbers are checked

Every figure the calculator uses is listed on the methodology page, with a link to where it comes from. The figures and the rules behind them are reviewed regularly. The last review was on 28 October 2026.

Independence

part-g.co.uk is independent. It isn't run by, or connected to, the government, any regulator or any product manufacturer. No installer or manufacturer pays to be mentioned, and I don't take work through the site.

Contact

Questions or corrections: hello@part-g.co.uk.