About Part G Online

What the App Does

The calculator guides users through the Appendix A methodology set out in Approved Document G, computing predicted water consumption in litres per person per day (L/p/d) for each dwelling in a development. You can enter detailed fixture specifications — WCs, basins, showers, baths, kitchen sinks — alongside appliances such as dishwashers and washing machines, optional systems like water softeners and waste disposal units, and any water-reuse measures such as rainwater harvesting or greywater recycling.

At the end of each calculation the tool applies the required 0.91 normalisation factor, adds the fixed 5 L/p/d external water allowance, and compares the result against the 125 L/p/d or 110 L/p/d target set by your local authority. You receive an instant pass/fail compliance result together with a full numerical breakdown, ready for submission to building control.

Who It Is For

• SAP assessors and energy consultants
• Architects and architectural technologists
• Planning consultants handling water-neutrality conditions
• Volume housebuilders managing large multi-plot schemes
• Self-builders wanting to confirm compliance before submitting for building regulations approval

Who Builds It

Part G Online is built and maintained by CoreLogic AI Ltd, a software company registered in England and Wales (No. 16919694). The platform forms part of the broader UKRAES suite of UK building-regulations compliance tools. Our goal is to make regulatory compliance faster, more accurate, and more accessible for every professional working in the UK construction industry.

The tool is updated in line with changes to Approved Document G and associated guidance. We welcome feedback from practitioners — if you spot an error or have a feature request, please get in touch.