Water efficiency calculations

What Are Water Efficiency Calculations?

According to the Building Regulations update from April 2010, requirement G2 states that any new build or conversion dwellings must have a water efficiency calculation completed on them. It states that ‘Reasonable provision must be made by the installation of fittings and fixed appliances that use water efficiently for the prevention of undue consumption of water.’

The regulations allow for a maximum of 125 litres of potable water per person per day. This comprises internal water use of 120 litres (per person per day) plus an allowance of 5 litres per person per day for outdoor water use.

Some local authorities will set lower targets, especially in London and the South.

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Why Should You Get Water Calculations Done?

Outside of them being specifically requested in the building regulations, it’s important that we all consider our impact on the environment.

By ensuring that your development complies with the maximum limit of 125 litres of potable water per person per day, you are also ensuring that you’re not contributing to excess water use.

Ethical reasons aside, using fittings with low flow-rates and capacities could mean you also make significant savings on your water bill.

Download Building Regulation Part G here:

Water calculations testing FAQ's

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We have learnt the importance of getting your Part G calculations completed at the design stage. It is far easier to change the bath you are planning on buying than it is to change the bath you have already bought and installed.

We’ve also found that the easiest ways to ensure a pass on your water efficiency calculations are to concentrate on the products with the highest use factor. A use factor is the multiplication applied to the capacity/flow rate of your fittings, based on how often they are likely to be used. Therefore, it’s good to be aware of the items that have a high use factor, and make those ones as energy efficient as possible.

For example, in a property with both a shower and a bath, the shower has a use factor (multiplication) of 4.37, compared to the bath’s use factor of 0.11. This is based on the assumption that showers get used an awful lot more than baths in most households. In this instance, it’s worth putting a lot of emphasis on purchasing a shower with a low flow rate.

We encourage you to have a chat with us for further information on water efficiency calculations.

Ideally these calculations should be carried out before you have purchased your proposed fittings so that your assessor can confirm whether these will meet Building Regulations compliance.

Don’t worry if you are already past this stage however, as there are other minor upgrades and attachments that can allow you to still meet the necessary rates.For a free, no commitment quote (or even just for professional advice) please feel free to contact us and we will be happy to help.

With clear and concise reports, quick turnaround (with a fast-track service available for even more urgent projects) why would you not?

Other reasons include:

  • Our team of qualified assessors go the extra mile to make the process as easy as possible
  • Design, guidance & advice throughout your entire construction phase
  • Guaranteed remedial advice in the event of failure
  • Simple explanations helping you cut through the jargon
  • Full reports provided, including a Notice of Water Efficiency (as required for Part G)

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    Our FAQ’s section offers the answers to a lot of the commonly asked questions.

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