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Water Calculations

New dwellings in England and Wales are required to demonstrate water usage of less than 125 litres per person per day. There are even more challenging targets under the New National Technical Standards of 110 litres per person per day.

In the Water calculation, information on features such as white goods, taps, showers, sizes of baths, grey and rainwater usage is used to reflect projected use.

Part G of the Building Regulations sets a whole building standard of 125 litres per person per day for domestic dwellings.  This allows 120 litres internal water use.  5 litres is allowed for outdoor use.

Part G breaks down the water requirements further, it states that:

  • Wholesome water must be provided as drinking water and for washing, whereas non wholesome water can be provided for WC flushing from rainwater harvesting, reclaimed water or water from wells or boreholes.
  • Hot water must be provided for washing and at any sink where food is likely to be prepared.
  • Thermostatic control of bath water is mandatory – it should not exceed 48oC
  • Any dwelling must have at least one bathroom with a fixed bath or shower.
  • Fixtures and fittings that are designed to limit the over use of water will be required – this applies to new buildings or a material change of use of a building. (for example a barn conversion).  Where no information on the actual model of appliance (such as dishwasher, washing machine, showers and taps etc) can be provided, assumed figures are given.

What we can do to help….

We pledge to get these calculations back to you within a couple of days and if needed, Carbon Green Consulting will advise you on how to reduce water usage and even what taps to use!

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If you'd like to talk to us about your project, do get in touch.