Reports for a scheme with a private water supply

A scheme that will rely on a private water supply needs two things the mains-connected equivalent does not. Evidence that the supply exists, yields enough and is fit to drink, and evidence that the foul drainage works on an unsewered site. Get either wrong and the permission arrives with an occupation condition you cannot discharge.

The planning reports themselves are not exotic. What changes is the evidence sitting behind them, and the fact that two regulators outside the planning system, the Environment Agency and the council's environmental health team, hold the answers you need.

Establishing the supply and proving the yield

Start with what is actually there. A borehole, a spring, a well or a shared supply from a neighbouring holding each have a different evidence trail, and the deeds often say something different from what the pipework does.

For a borehole, the drilling log matters. Boreholes over a certain depth must be notified to the British Geological Survey under section 199 of the Water Resources Act 1991, so historic logs for the area may already exist and are worth ordering before you commission anything.

Yield is the number the case officer will look for. A pumping test carried out by the driller, reported in litres per second or cubic metres per day, with a drawdown curve and a recovery period, is the evidence. A spring needs seasonal flow measurement instead, ideally including a late summer reading, because a spring measured in February tells you very little about August.

Set the yield against demand honestly. A water supply assessment that compares measured yield with the occupancy the scheme creates, including peak day rather than average day, is the document that answers the officer's question.

Water quality, treatment and the environmental health team

Quality is assessed by the local authority, not the planning department. Private supplies in England are regulated under the private water supply regulations, which place a duty on the council to risk assess and sample supplies, with different regimes for single domestic supplies, small shared supplies and commercial or large supplies.

That distinction matters at planning stage. A new dwelling served by its own borehole falls into a lighter regime than a holiday let, a campsite or a food business on the same water, and the sampling regime and the treatment you have to install differ accordingly.

Expect to provide a bacteriological and chemical analysis from an accredited laboratory, taken at the tap rather than at the source, and a description of the treatment train. Ultraviolet disinfection with pre-filtration is the common answer for a small supply, with additional treatment where iron, manganese, nitrate or arsenic show up in the analysis.

Where the borehole sits inside a groundwater source protection zone, the Environment Agency's position on activities near the source becomes a material consideration, and any proposal involving fuel storage, foul drainage or hardstanding close by will be looked at harder.

Abstraction licensing and where the threshold sits

Abstraction of more than 20 cubic metres a day from a source needs an abstraction licence from the Environment Agency under the Water Resources Act 1991. Below that figure the abstraction is generally exempt, which is why most single dwellings and small conversions never need one.

The threshold catches people out on cumulative schemes. Five holiday units, a farm shop and a café on the same borehole can pass 20 cubic metres a day on a summer weekend even though each element looks trivial on its own.

Two practical points. A licence application runs on its own timetable and is not granted because planning permission exists, so a scheme that needs one should start the conversation with the Environment Agency in parallel with the planning application rather than afterwards. And where the source is hydrologically connected to a designated site, the licence assessment can raise habitats issues that feed straight back into the planning decision.

Foul drainage on an unsewered site

The drainage hierarchy in national planning guidance puts connection to the public sewer first, then a package treatment plant, then a septic tank. Departing from that order requires justification, usually a distance and cost comparison for connecting to the nearest sewer.

Discharges from a small sewage treatment system are controlled separately under the environmental permitting regime. The general binding rules allow a discharge within stated volume limits and siting restrictions without a permit, and a discharge that breaches those rules, or that sits in a sensitive location, needs a permit instead.

Septic tanks discharging directly to a surface watercourse are no longer allowed under the binding rules, which is the single most common problem on a conversion of an older property. The existing arrangement has to be replaced with a treatment plant or a drainage field, and that has land take, percolation testing and cost implications the application should show rather than hide.

A foul sewage assessment covering the proposed system, the percolation test results to the relevant British Standard, the drainage field size and the separation distances to the borehole, boundaries and watercourses answers most of this in one document.

Keeping the supply and the drainage apart

The geometry of an unsewered site is a design problem, not a paperwork problem. A drainage field needs separation from any source used for drinking water, from watercourses and from buildings and boundaries, and those distances often conflict with the plot layout an architect has already drawn.

Work it the other way round. Fix the borehole position and the drainage field position first, then place the building. On a tight plot this decides whether the scheme is viable at all, and finding out at reserved matters stage is expensive.

Percolation testing has to be done in representative conditions. A test dug in a dry August on clay will give an answer that does not survive the winter, and building control will pick it up even if planning does not.

Shared supplies and the legal rights behind them

Where the supply crosses land you do not own, the planning application still has to be accompanied by the right ownership certificate, and the practical question is whether you have a right to take water and to maintain the pipe.

Look for an express easement in the title, a deed of grant, or a long-standing arrangement capable of amounting to a prescriptive right. An informal agreement with a neighbour is not evidence a council can rely on when it is deciding whether the dwelling will have a lawful supply.

Shared supplies also bring shared responsibility for sampling and maintenance. Councils increasingly ask for a written management arrangement between the parties, setting out who tests, who maintains the treatment and who pays, before they will accept the supply as adequate.

Conditions on occupation and how to discharge them

Expect a condition that no dwelling is occupied until a potable supply has been provided and tested to the satisfaction of the authority, and often a second condition covering the foul system.

Plan for the discharge at the start. Keep the pumping test report, the laboratory analysis, the treatment specification and the commissioning certificate in one pack, and submit them together rather than in instalments. Each partial submission restarts the officer's clock.

Where the case is finely balanced, offering a condition yourself in the planning statement is often better than waiting for one to be imposed, because you can shape the wording to something you can actually satisfy. That is the same discipline described in the pack for a self-build plot in a conservation area, where the evidence runs ahead of the decision rather than behind it.

This is general guidance, not legal advice, and the position on abstraction, permitting and private supply regulation should be checked with your local planning authority, the Environment Agency and a qualified professional before you rely on it.

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