Part G Water Efficiency Calculations
New homes must meet water-use limits under Approved Document G of the Building Regulations. Part G water efficiency calculations ensure residential designs comply with daily water consumption targets, supporting sustainability and smooth regulatory approval for developers, architects, and self-builders.
What are Part G Water Efficiency Calculations?
A Part G calculation predicts average daily water use per occupant by assessing all sanitary fixtures and appliances. The standard target is 125 litres/person/day, but some local planning bodies, especially in London and the South East, may require lower consumption, such as the London Plan’s current 110 litres/person/day target, ensuring designs meet local and national regulations.
What Information Do I Need to Provide?
At design stage, you will need to supply floor plans showing all wet rooms, including kitchens, utility areas, and bathrooms. These plans must also indicate the number and type of water-using points such as WCs, showers, sinks, dishwashers, and washing machines.
At as-built stage, we require the final construction drawings along with a completed confirmation sheet outlining the exact fixtures installed and their flow rates. This allows us to verify that the finished property meets the predicted water-use targets.
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Key Fixtures & Flow Rates We Calculate
To accurately calculate water efficiency, we need details of all relevant fixtures, appliances, and their flow rates. This ensures predicted water use per occupant is precise. Key items considered include:
Bathroom, kitchen, & utility taps
Showers & baths (including bath volume)
WCs
Dishwashers & washing machines
Waste disposal units
Water softeners
Rainwater & greywater harvesting systems
Why Water Efficiency Matters
Meeting Part G standards reduces water waste, lowers utility bills, and enhances sustainability. Proper water efficiency planning ensures homes are responsibly built and compliant, giving homeowners confidence in their property’s environmental performance
Expert Part G Compliance Support
We model your project using approved Part G methodology, calculating daily water use per occupant and checking it against required targets. If consumption exceeds limits, we recommend practical adjustments to fixtures or flow rates. With experience delivering Part G calculations since 2015, our in-house team provides clear guidance and tailored support throughout your project.
Ready to Comply with Part G?
Let Melin Energy Consultants handle your water efficiency calculations and deliver a clear, compliant report. Contact us today to ensure your new build or conversion meets Part G requirements with accuracy, efficiency, and sustainability in mind.