Private water supply assessment

Last Updated: 24 April 2023

Where a proposed development is to be served by a private water supply, the applicant should demonstrate that the water supply is sufficient (even in times of prolonged dry weather), wholesome and safe to drink and does not compromise the adequacy of other private water supplies in the area.

When required

All development that may materially increase demand on the private water supply. For example, new dwellings, barn conversions, commercial buildings/extensions or some domestic extensions etc.

Contents of private water supply assessment

The applicant must submit a report from a suitably qualified and competent person which identifies the source of the private water supply, the proposed treatment process and demonstrates the capability of the treatment system to achieve a sufficient and wholesome supply of water in accordance with Regulation 4 of the Private Water Supplies (England) Regulations 2016 (as amended).

The written report from a competent person should confirm the flow rate (usually in litres per minute) from the source, in other words, the water available and demonstrate that this will be sufficient to supply all premises on the supply. This is nominally calculated at 200 litres per person per day at max occupancy. So if there will be four premises each with a max occupancy of 5 people it will be 20 x 200 litres which is 4000 litres or 4 cubic metres per day.

The most important thing is whether there will be enough water. This is particularly important where there are existing users on a supply who may be rightly concerned that adding premises or increasing demand may reduce the amount of water available to them.

The local authority has a statutory duty to risk assess and monitor all commercial and small shared supplies to ensure that the water supply meets all of the prescribed concentrations or values set out in the Private Water Supplies (England) Regulations 2016 (as amended).

If the water supply is not a mains supply, please complete our private water supply assessment form (PDF 166KB / 2 pages).


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