The Building Services Portal Water Efficiency Calculator

The Building Services Portal water efficiency calculator is a spreadsheet template used for demonstrating compliance to the Building Regulations Part G requirements for new dwellings. The spreadsheet is extremely simple to use with accompanying instruction to guide you through the process. Get started straight away with the below embedded spreadsheet (desktop and tablet only) or download the full version for free which includes the Building Services Portal guidance notes.


Please be patient as the spreadsheet loads..


The cells that require you to enter values are highlighted in yellow. The sheet automatically calculates the relevant totals. Embedded above is table A1, there are further tables required for more complex systems, these are included in the downloadable free spreadsheet. Further instructions and useful general pump sizing tips are contained within the downloadable free spreadsheet in the link below. Also see below for the premium version.

Water Efficiency Calcualtor options


£ Free


  • Excel format
  • Download now or try using the embedded spreadsheet above
  • Clear easy to follow instructions included
  • Building Services Portal tips included
  • Easy to use


£ 49 (incl. VAT)

All features of the basic version plus…

  • Features your company logo and watermark removed for professional presentation of your calculations, ideal for Building Regulation Part G compliance submission.
  • Customer support- Our team of Chartered Engineers respond to all product related questions within 1 working day

Design Pack

£ 198 (incl. VAT)

fan sizing pump sizing design pack box

Premium Design Pack Includes…

  • The Premium Building Services Portal Water Efficiency Calculator
  • The Premium Building Services Portal Pump sizer spreadsheet
  • The Premium Building Services Portal Fan sizer spreadsheet
  • Building Services Portal 32 GB USB memory stick
  • Free delivery
  • 90-Day money back guarantee

Further water efficiency calculator details...

Free Version

Easy to Use

The Building Services Portal Water Efficiency Calculator is the easy way to carry out the required Building Regulation Part G Water Efficiency Calculations for new build residential properties. Calculations are presented in a professional manor suitable for Building Regulation compliance submission.

Simply enter the relevant product data for the properties sanitaryware and appliances then calculator will do the rest. The total water consumption per person/ per day, is calculated using the Building Regulation Part G methods, from entering the below information;

  • WC flushing volumes
  • Tap flow rates
  • Bath capacities
  • Shower flow rates
  • Sink tap flow rates
  • Washing machine/ dishwasher/ waste disposal units and water softener information

There is no need for carrying out complex calculations, all required values are calculated automatically! 

Instructions and general guidance is included

The water efficiency calculator spreadsheet includes detailed instructions for use and general advice. Various tables for calculating situations with multiple types of each sanitaryware items are included. The calculator also includes all calculations required for rainwater and greywater harvesting systems. Simply click on the relevant tab at the bottom of the page to display the different sheets which all contain helpful guidance.

Download the free version now to experience the easy to use calculation tables. 

Premium version

Present your calculations professionally

The Premium version is ideal for professionally presenting your calculations. The Premium version includes your company logo which makes it ideal for presenting calculations to clients and for Building Control submission. Your logo will be in place of the Building Services Portal logo.

The Premium version comes with the added benefit of customer support. Our team of Chartered Engineers will respond to any questions related to the water efficiency calculator within 1 working day.

We are confident you will be happy with your purchase but offer a no quibble 90-day money back guarantee.

Premium Water Efficiency Calculator- £49 (incl. VAT)

Building Services Portal- Premium Design Pack

The Premium Design Pack includes the following;

  • The Building Services Portal Water Efficiency Calculator
  • The Building Services Portal Premium Pump Sizer
  • The Building Services Portal Premium Fan Sizer
  • Building Services Portal 32GB USB Memory stick
  • Customer Support
  • 90-Day Money Back Guarantee

Premium Design Pack- £198 (incl. VAT)

The Building Services Portal Pump Sizer is powered by Microsoft Excel