Part G: Water Efficiency Calculation

Under Part G of the Building Regulations, all new dwellings must demonstrate water efficiency, typically aiming for a maximum usage of 125 litres per person per day, with some local authorities requiring a reduced usage of 110 litres per person per day.

Our service provides fast, accurate calculations using the official methodology set out in Appendix A of Part G 2015, ensuring your project meets compliance with minimal hassle. Whether you're working on a single plot or a multi-unit development, we deliver clear documentation ready for Building Control, with optional guidance on fittings and flow rates to help optimise performance.

Note: It is possible to be compliant without the calculation by following The Fittings Method. The Fittings Method calculates water consumption based on the flow rates and capacities of individual fixtures—such as taps, showers, toilets, and appliances. It’s suitable for most new dwellings and conversions, provided the fittings are specified at design stage. All fittings must comply with the performance criteria listed in Table 2.1 of the Part G guidance, ensuring consistency and accuracy in the assessment. This method allows for flexibility in product selection while demonstrating compliance with the daily water usage target. If a fitting does not comply or optional extras are used (water softeners etc) then a water efficiency calculation must be completed to comply with the requirements.