Water Efficiency Calculations Building Regulations Part G & Planning Conditions
Got a planning condition requiring 110 litres per person per day? We produce the water efficiency calculation to Building Regulations Part G and the optional standard, and the report to discharge your condition — usually within 48 hours.
Water Efficiency Calculations for Planning & Building Control
New dwellings in England must meet a water efficiency standard under Part G of the Building Regulations — a baseline of 125 litres per person per day, or the tighter optional standard of 110 litres per person per day where a planning condition requires it (commonly in water-stressed areas). The figure has to be demonstrated by calculation, and a planning condition is not discharged until that calculation is provided.
We prepare the water efficiency calculation using the Government’s fittings-based methodology, specify the tap, shower, WC, bath and appliance flow rates needed to hit your target, and produce a concise report ready to submit to the LPA or Building Control. If your current fittings schedule doesn’t comply, we tell you exactly what to change to get there.
What’s Included
- ✓ Fittings-based calculation — the per-capita consumption worked through using the Part G methodology and your sanitaryware schedule
- ✓ 110 or 125 l/p/d target — whichever your condition or Building Control requires, clearly demonstrated as a pass
- ✓ Fittings specification — the maximum flow and flush rates required for taps, showers, WCs, baths, dishwashers and washing machines
- ✓ Rainwater / greywater credit — where harvesting or reuse is proposed, the allowable contribution applied to the calculation
- ✓ Condition discharge report — a submission-ready report referencing the relevant condition and Part G optional requirement
- ✓ Multiple house types — a calculation per dwelling type across a site, not just a single worked example
When Do You Need a Water Efficiency Calculation?
Send us the condition wording and your fittings schedule and we’ll do the rest. Get a free quote.
Planning Condition for 110 l/p/d
Many LPAs impose a condition requiring the optional 110 l/p/d standard. The calculation is the evidence required to discharge it before occupation.
Building Regulations Compliance
Every new dwelling must demonstrate Part G water efficiency to Building Control — the calculation forms part of the compliance package.
New Build Housing Sites
On multi-unit sites a calculation is needed for each house type. We handle the full set in one report.
Conversions & Change of Use
New dwellings created through conversion or change of use are also caught by Part G and frequently by a water efficiency condition.
Water-Stressed Areas
In designated water-stressed areas the tighter 110 l/p/d standard is increasingly the default planning expectation rather than the exception.
Paired with Drainage Work
Already commissioning an FRA or drainage strategy from us? We can add the water efficiency calculation at the same time for a reduced combined fee.
Frequently Asked Questions
Get a Free Quote
Free, no-obligation fixed-fee quote within 24 hours. All flood zones and LLFAs covered across England and Wales.
Get a Free QuoteOr contact us directly: 07826 705389 •