Toilets1 of 5
Editing specificationMake your changes, then recalculate to update your result.

Part G Water Efficiency Calculator

Check your new dwelling against the 125 or 110 L/person/day requirement.

No account required. Enter your proposed fittings and we’ll guide you through the calculation.

Free calculation Instant PASS / FAIL Approved Document G methodology
How would you like to calculate?Quick is designed for most users. Advanced lets you enter exact manufacturer specifications.
What are you calculating?
Please choose what you are calculating before you continue.
What you'll need

Just tell us how many toilets, taps, baths and showers the property has. We’ll apply a standard specification and the official appliance defaults for a quick Part G check.

Set up your development

Start with the development name and the Part G requirement. House types come next.

You can add the site address later when preparing the Building Control reports.

Required

Part G requirement for this development

All house types will use this requirement.

Add your house types

Group together plots that use the same water specification.

Development125 L/person/day
House type

Add your first house type

Plots using the same fittings can be grouped together.

More details (optional)
Your house types0 house types · 0 plots
House type saved

Do you have another house type?

All plots using the same water specification can stay grouped together.

Check your development

Make sure the house types and plots below are correct before entering the water specifications.

Development
House type 1 of 1House type
Water specification
Quick calculator

Tell us what the property has

No flow rates or flush volumes needed. We’ll use the standard quick-calculator assumptions shown below.

Quick mode assumptionsDual-flush toilet 6 / 4 L · wash-hand basins 6 L/min · kitchen/utility sinks 8 L/min · shower 10 L/min · bath 185 L · official appliance defaults.
Required

Which Part G requirement applies?

Choose the maximum permitted water consumption for this dwelling.

Toilets

If all toilets are the same, enter one specification and the quantity. Add another type only when the specification differs.

Where do I find this?

Use the manufacturer's full and reduced flush volumes for a dual-flush WC, or the flush volume for a single-flush WC.

Taps & sinks

Enter the manufacturer flow rate for each different fitting.

Wash-hand Basins

Where do I find the tap flow rate?

Check the manufacturer product page or technical data sheet and look for “flow rate”, normally shown in litres per minute (L/min).

Kitchen & Utility Sinks

Where do I find the flow rate?

Look for “flow rate” in L/min on the product page or technical data sheet.

Baths & showers

Tell us what is installed and we’ll only show the information that applies. If there is a shower over a bath, count both the shower and the bath.

Does the property have a bath?

Use the manufacturer's capacity to overflow in litres.

Does the property have a shower?

Use the manufacturer's flow rate in L/min.

Appliances

Don’t know the appliance specification yet? Choose “No / not yet” and we’ll use the official Approved Document G default.

Has a washing machine specification been selected?

✓ Official default will be used: 8.17 L/kg dry load.

Has a dishwasher specification been selected?

✓ Official default will be used: 1.25 L/place setting.

Anything else?

Most properties can answer No to these and continue in a few seconds.

Kitchen waste disposal unit?
Ion-exchange water softener that uses water?
Calculated occupancy

— occupants, using the Appendix A bedroom-based occupancy rule.

Rainwater harvesting or greywater recycling system?

Choose No if the property has neither system.

Advanced water-reuse system

Only the additional information required by the Appendix A calculation is shown.

Occupancy is based on two occupants in the first bedroom and one in each additional bedroom; a studio is treated as two occupants.

Greywater recycling

Collected from
Used to supply

Rainwater harvesting

Used to supply

That's everything

Have a quick check, choose the requirement for the project, then we’ll calculate your result.

Required

Choose your project requirement

Select one before calculating. If Building Control or the planning documents have not specified the tighter option, the standard requirement will normally apply.

You must choose one of these two options to continue.

Review your specification

You can go back and change anything before calculating.

Next house type

Next house type

How would you like to start this water specification?

Select an option, then continue.

Part G water-efficiency result
litres per person per day
0
Server-verified Part G calculation

Why did it fail?

These are the largest contributors in the entered specification. This does not mean a product is defective; it shows where a design change has the greatest influence on the calculation.

Ways to achieve compliance

The options below have been recalculated against your specification. An option is only marked PASS where that change would bring the dwelling within the selected maximum.

View calculation breakdown

Water reuse contribution

Project setup

Your calculation has passed. Review the project setup below before creating the report package.

PASS
House type complete

This house type passes

Your verified specification has been completed.

PASS
Verified result
Your development0 house types · 0 plots

Saved house types

Get your Building Control reports

Your calculation is complete. Add the report details below and generate the supporting documents for Building Control.

PASS only
Report details
Development details

Individual plot numbers and addresses are taken automatically from the house types and plots you entered above.

Your company branding (optional)

Useful for architects, consultants and developers who want the report issued in their own branding.

Company logo preview
One final step

Complete your plot addresses

Each plot needs the address that should appear on its individual Building Control report.

0 of 0 complete
Report package
1. Water Efficiency Report Formal PASS summary for Building Control, including project details, selected requirement and final consumption.
2. Part G Calculation Schedule Full fittings/appliances schedule, component contributions, water-reuse deductions and Appendix A calculation trail.
Official report package£20.00 + VAT
One dwelling · £24.00 including VAT

Your result is free. You only pay if you want the official Building Control PDF reports. An account is created or used securely at checkout.

Individual reports Prefer separate PDFs? Download either document below.
Water Efficiency Report Main PASS report prepared for Building Control.
Part G Calculation Schedule Detailed supporting calculation and specification schedule.

Part G water-efficiency documents prepared for submission to Building Control. This is not a government-issued certificate, accreditation or approval.

Report cannot be generated yet

Amend the specification using the suggestions above, recalculate, and the PDF report will unlock once the result passes.

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