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Water Calculations


We provide a fast turnaround on water calculation for new build houses throughout the UK. Use our worksheet to make it easier than ever.

The Regulations

Part G of the Building Regulations state that all new dwellings must be shown to use less than 125 litres of water per person per day. In some cases, this may be reduced to 105 litres depending on your local authority.

This can be demonstrated by supplying Building Control with a set of bespoke water efficiency calculations.

When should you get your calculations done?

  1. The products going to be used
  2. Before purchasing products
  3. A clear idea of the number of fittings

Following these 3 rules allows for the flexibility if any alterations need to be made.

How we help

Once we have the information we can begin with the calculations. If the requirements are met, we provide a report providing clear information for both you and building control.

Sometimes additional products or substitutions may be needed, We can suggest solutions and products which are efficient, practical and cost effective.

Information Needed

The calculation involves internal ‘potable’ water and accounts for the number and type of the following products:

  • Toilets
  • Taps
  • Baths
  • Showers
  • Washing Machines
  • Dishwashers
  • Rainwater Recycling
  • Water Softener
  • Grey Water Recycling
  • Waste Water Disposal


Airtight testing Staffordshire are here to help you move quickly and easily through the process. Our experienced consultants can offer expert advice to achieve compliance.

We can also offer a wide range of services to pass building regulations easier than ever before!