Water calculations

Photo credit: Whitecroft Developments Ltd

Within 25 years England will not have enough water to meet demand, the head of the Environment Agency has warned.

Sir James Bevan wants wasting water to become “as socially unacceptable as blowing smoke in the face of a baby”.

The career diplomat has warned that unless we act now, in around 20-25 years we will reach the “jaws of death”, the point at which we will not have enough water to supply our needs.

With the Energy Saving Trust warning that 12 out of 23 water companies in England operate in areas rated as being under “serious water stress”, water calculations are a vital part of building a better future.

Dwellings need to demonstrate that they use no more than 125 litres/person/day.

We have completed many different Part G calculations, including calculations incorporating rainwater and greywater systems.

What do these calculations do?

  • Part G calculations assess what plumbed services are present in a building and their individual water use based on capacity and / or flow rate.
  • These services are then combined to determine whether or not the property as a whole falls below the maximum water use required under Part G of building regulations or respective local council requirements, which may improve upon building regulations.

Top tips

  1. Use flow restrictors on taps and showers One of the most cost-effective ways to comply with the Part G regulations is the use of flow restrictors on taps and showers.These flow restrictors can be fitted in the pipework and can ensure lower flow rates for these fixtures and fittings.
  2. Install rainwater or grey water systems Rainwater and grey water systems are a great solution to enable buildings to achieve less than 100 litres / person / day. Potable water usage levels lower than 100 litres / person / day are best achieved through the incorporation of rainwater or greywater systems.
  3. Think about how Part G and Part L in the round Under the new regulations the critical value for showers will be 8 litres per minute, so you should design the shower flow rates to maximize how Part G and Part L affect one another.

Next steps

We can conduct the formal calculations required by Building Control as well as suggest amendments to meet specifications. Get in touch to find out more.
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