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    Water Use Calculation

Residential Services / Water Use Calculations

Part G of the Building Regulations requires all new homes and converted properties to achieve a maximum water usage of 125 litres per person per day. Water use is determined by a Water Efficiency Calculation which needs to be submitted to the Building Control Body (Approved Inspector or Local Authority Building Control). The calculations are also a requirement of the Code for Sustainable Homes.

We provide fully compliant reports and calculations for Building Regulations and Code for Sustainable Homes Assessments. We pride ourselves in delivering a personal service with a commitment to clear and cost effective advice.

Here some points to consider before appointing someone to undertake your calculations:

  • We provide a full consultation service as standard – all the advice and support you need to ensure you meet the required level of performance.
  • Full report and calculations included in our standard fee – there are no hidden extras!
  • Calculations are carried out by experienced construction professionals – providing cost effective and practical solutions.

Call now to get a quote or discuss your project with one of our team.

Why is water efficiency important?

Climate change may result in increased variability in weather patterns, increasing both the risk of flooding and extended dry spells. Water is becoming scarcer at the same time as the population and demand for water is increasing, as a result water consumption is likely to become an increasing national problem.

Research carried out by the Environment Agency has found that 20% of the UK's water is consumed domestically, with 50% of this used for flushing WC's and washing. The development of practical ways to reduce water consumption is important to ensure levels of supply can be maintained into the future.

What do the Building Regulations require?

On the 6th April 2010, Part G of the Building Regulations introduced a requirement for a water efficiency calculation to be carried out for every new dwelling. A calculation is required to show the potential consumption of wholesome water per person per day. The calculation is based on fixtures and fittings in a dwelling as well as any grey water or rainwater harvesting technologies.

Each new dwelling is required to have a maximum consumption of 125 litres per person per day to comply with Building Regulations.

What does the Code for Sustainable Homes require?

Indoor water use is one of the mandatory categories of the Code for Sustainable Homes. The required level of water efficiency increases with additional stars:

  • Level 1 & 2: <=120 litres per person per day
  • Level 3 & 4: <=105 litres per person per day
  • Level 5 & 6: <=80 litres per person per day

Failure to achieve the levels of water efficiency given above may mean that the required Code for Sustainable Homes rating is not achieved.

What affects the projected water consumption of a dwelling?

Factors that affect the calculated water consumption of a dwelling include:

  • The flow rate of showers and taps;
  • The capacity of baths;
  • The flushing capacity of WCs;
  • The consumption per place setting of dishwashers;
  • The consumption per kilogram of dry load for washing machines;
  • The efficiency of water softeners (where present); and
  • Whether there is any on-site rainwater or grey water harvesting.

External taps, bath taps, swimming pools, Jacuzzis and bidets are not included in the calculation process.

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Contact us

PB Sustainability Ltd.

Office 64
The Old School
Wallasey, Wirral
Merseyside
CH44 5TN