Water Efficiency Calculations (Part G)
Fast, accurate Part G assessments for new builds, conversions & extensions
Prices Start from £45.00
Why do you need Water Efficiency Calculations?
Building Control cannot sign off a new dwelling unless a compliant calculation is submitted. They ensure the home meets the national water‑efficiency target. This is why we recommend every SAP package for new builds includes a Part G assessment.
When should you get your Water Efficiency Calculation?
You need it twice:
Design stage – A design-stage calculation checks your chosen fittings will comply before you buy anything. This avoids delays, prevents non‑compliant choices, and ensures your project meets the required water‑use limit from the start.
Completion – Once the property is complete, an as‑built calculation confirms the installed fittings meet the standard. Building Control will require this before issuing your completion certificate.
Get your Water Efficiency Calculation early to avoid problems, and again at completion to prove compliance.
What do we need from you?
To complete your Water Efficiency Calculation, simply provide:
Tap and shower flow rates
WC flush volumes
Bath capacity
Appliance details (if known)
Any rainwater or greywater systems
Alternatively at design stage if you send us your architectural plans we can use this to determine the number of fittings and use standard values to create a calculation and recommendation for compliance.
Get your Water Efficiency Calculation sorted quickly and keep your project moving. Send your details/plans today for a fast, fixed‑price quote.
What is a Water Efficiency Calculation?
A Water Efficiency Calculation is required under Approved Document G for all new dwellings. It measures the predicted daily water use of your home based on the flow rates and capacities of taps, showers, toilets, baths and appliances.
Every new home must meet the national limit of 125 litres per person per day, or 110 L/p/d where local planning requires a tighter standard.
At New Build SAP, we provide fast, accurate Part G calculations at both design stage and as‑built, ensuring smooth Building Control approval.