Building Regs Part G • 110 / 125 l/person/day • Condition Discharge

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.

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Part G compliant
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110 & 125 l/p/d
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Fittings-based calculation
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Condition discharge report
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48-hour turnaround

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
Water-efficient tap fitting Running tap water Water conservation

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.

Part G Water Efficiency Explained

The calculation that shows a new home meets its water-use standard.

Building Regulations Part G requires new dwellings to be designed to a maximum water consumption of 125 litres per person per day, and many local plans apply the tighter optional standard of 110 l/p/d in water-stressed areas. A water efficiency calculation uses the government's Water Efficiency Calculator to demonstrate compliance from the specified fittings — and is frequently required by planning condition before occupation.

The 125 vs 110 standard

The default Part G limit is 125 l/p/d; local plans in water-stressed regions (much of the south and east) require the optional 110 l/p/d standard. We confirm which applies to your site from the local plan and any condition.

How the calculation works

Flow rates and capacities of the specified taps, showers, WCs, baths and appliances are entered into the calculator, which produces the predicted consumption. Rainwater or greywater reuse can be credited where used.

What we provide

A completed calculation and compliance statement for Building Control and the planning condition, with a schedule of fittings your plumber can work to.

Frequently Asked Questions

What’s the difference between 125 and 110 litres per person per day?
125 l/p/d is the mandatory Building Regulations baseline for new homes in England. 110 l/p/d is the optional tighter standard that applies only when a planning condition requires it — it demands more efficient fittings to achieve.
How is the calculation done?
We use the Government’s fittings-based approach: the flow or flush rate of each water-using fitting is entered into the standard methodology to produce a calculated per-capita consumption, which must be at or below your target.
My fittings don’t comply — what now?
We tell you exactly which fittings to change and the maximum flow rates needed. Usually small specification tweaks — a lower-flow shower or tap aerators — are enough to bring a dwelling within the standard.
Does rainwater harvesting help?
Yes — where rainwater harvesting or greywater reuse is installed, an allowance can be credited in the calculation, which can make a demanding 110 l/p/d target easier to achieve.
How quickly can you turn it around?
A water efficiency calculation and condition discharge report is usually delivered within 48 hours of receiving your fittings schedule. We’ll confirm a fixed fee within 24 hours of your enquiry.
When is a water efficiency calculation needed?
For all new dwellings under Part G, and specifically wherever a planning condition requires proof of the 110 l/p/d optional standard — typically in water-stressed areas designated by the Environment Agency.
What is the difference between 110 and 125 litres per person per day?
125 l/p/d is the national Building Regulations default; 110 l/p/d is the optional, stricter requirement that local planning authorities can impose in water-stressed areas. Meeting 110 usually means specifying lower-flow taps and showers and dual-flush WCs.
What information do you need from me?
The number of dwellings and the proposed fittings (or we can specify a compliant schedule for you), plus the planning condition wording so we address exactly what the council has asked for.

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Free, no-obligation fixed-fee quote within 24 hours. All flood zones and LLFAs covered across England and Wales.

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