How safe is your private water supply?

Written by Susan Keogh

Water testing

The purpose of this blog, is to provide information to the owners and users of private water supplies on:

  • The potential risks in using a private water supply;
  • How to assess and protect against these risks; and
  • How to get more advice on your private water supply.

What is a private water supply?

A private water supply is any supply of water not provided by the public (mains) water supplier.   A Supply may serve a single property, many properties or a commercial business.

What can be the problem?

Safe drinking water is essential to good health. All private water supplies can pose a threat to health unless they are properly protected, treated and maintained. They may become contaminated with bacteria, protozoa, parasites and viruses (micro-organisms) or other substances. Many of these are harmless, but some can cause serious illness or even death in vulnerable groups of people. You may not be able to tell whether your water is contaminated as it may not change the smell, taste or colour of the water. Unlike public supplies, many small private supplies are not treated to remove contamination. This blog explains a number of things you can do to protect your supply and reduce the risk of contamination.

What is the role of the Drinking Water Inspectorate?

The Drinking Water Inspectorate (DWI) is responsible for the monitoring and regulation of private water supplies to commercial or public premises or groups of domestic houses (excluding single domestic dwellings) where the water is used for drinking, washing, cooking or the production of food/drink. If your private water supply is in one of these categories then you are required to register your supply with your local council under the private water supplies regulations.

The DWI can offer advice to the owners/users of all private water supplies, including those to single domestic dwellings. This advice can cover protection of your source, storage and distribution of your water, as well as providing details on the different treatment options available to owners/users of private water supplies.

Types of Private Supplies

Springs, boreholes and deep wells that draw water from deep underground sources are less likely to be contaminated than supplies from other sources but water may become contaminated where:

  • The spring emerges; or
  • The water collects in the borehole or well.

In farmland, underground water can pick up nitrates (from fertilisers) or pesticides which may be harmful to health. Water from shallow wells, and springs which draw water from close to the surface of the ground, is usually less wholesome and more likely to be contaminated.

Streams, Rivers and Lakes

The quality of water from streams, rivers and lakes will generally not be as good as that from springs, boreholes and deep wells. The quality of this water will also vary depending on the weather conditions. It is highly likely to be contaminated, particularly with bacteria, at times of:

  • High rainfall; or
  • Warm weather.

Water that runs across land into streams, rivers and lakes picks up contamination from various sources, for example, the soil and the droppings from farm animals, wild animals and birds. Some of this contamination may be dangerous to health.

Also contamination from pollution events puts these sources at high risk.

Is your private water supply safe?

A number of serious illnesses can be contracted from water contaminated with micro-organisms (bacteria, viruses, parasites and protozoa). The most likely source of contamination of the water will be animal droppings. Water supplies drawn from farmed land where animals graze or where manure is spread are at most risk. The risk is particularly high at times of heavy rainfall, when water may run directly off farmland and carry micro-organisms into private water supplies.

To reduce the risk of bacterial contamination, it is advised that slurry should not be spread within 50 metres of a borehole, spring or well. In addition, the location of septic tanks should be checked to ensure that any discharge is directed away from drinking water sources.

People who do not drink the private water supply regularly and are not used to it, such as visitors and guests, may be at greatest risk of infection from micro-organisms in the water.


Private water supplies may be affected by chemicals used in:

  • Farming or forestry (for example, fertilisers, pesticides and sheep-dip); or
  • Old industrial premises or workshops.


Pesticides should not be sprayed or stored in the vicinity of drinking water sources. The buffer zone distances recommended by the manufacturers of pesticides should always be observed. Advice should be sought on the disposal of waste pesticides and sheep dips so as to prevent contamination of private water supplies.


Water containing high levels of nitrates may not be suitable for:

  • Young children;
  • Bottle-fed infants; or
  • Pregnant women.


Some private water supplies are naturally acidic and may dissolve lead. If your supply passes through a lead tank or pipes, either outside or inside the home, it is possible there will be a significant amount of dissolved lead in your water. Due to the health risks associated with lead you should replace any lead pipes, fittings or tanks.

Other Materials

Some water contains naturally occurring materials picked up from the ground such as iron or manganese. These may affect the appearance, taste or smell of the water. On the whole, these are not necessarily dangerous to health but could make any disinfection treatment installed on your supply less effective.

Keeping Your Supply Safe

Find Out About Your Supply:

Who is responsible for the upkeep and maintenance (if this is not clear, consider reaching an agreement with the other users)?

  • Where is the source?
  • How does it get to your property?
  • Is it treated in any way?
  • Is the treatment equipment in good order and maintained and serviced regularly?
  • Has your supply been tested?

Source Protection:

  • Check that the source is adequately protected by watertight covers to stop surface water entering your supply, particularly at times of heavy rain.
  • Ensure that the water being collected is not contaminated by discharges from a septic tank, or slurry spreading, or any nearby sources of pollution e.g pesticide or oil storage.
  • Check that neighbouring farmers are aware of the drinking water supply and the need to avoid contaminating it by farming activities. Fencing may be necessary to stop farm and other animals from interfering with the source.
  • Divert rain-water run-off so it does not flow into your supply (for example, with a small ditch leading away from your supply).

Pipe Work and Storage Tanks:

Check that pipe work bringing the water from your source is in good condition, does not leak and is protected from being damaged by weather, animals or farm machinery.

  • Storage tanks should have watertight walls and lids.
  • Overflow pipes or vents should be protected by a suitable mesh to prevent smallanimals entering the tank/chamber.
  • A schedule should be put in place for regular checking and maintenance of pipework and storage tanks.

Water Treatment:

  • Treatment installed on your supply should be maintained and serviced as recommended by the manufacturer.
  • UV treatment should be regularly checked to ensure it is operating correctly and the pre-filter replaced, as required, dependent on the quality of the source water.
  • UV lamps should be routinely replaced, normally annually.
  • Where chlorination is used to disinfect the supply, controls should be in place to maintain the required levels of chlorine at all times, especially over weekends.
  • Treatment/disinfection in place should be sufficient to adequately treat the water even during periods when your water quality may be poor.

Water Quality Testing

  • Private water supplies registered with the DWI under the private water supplies regulations will be tested and the results provided to the owners/users.
  • For private supplies to single domestic dwellings, you should contact the environmental health department of the local council to request a sample to be taken.
  • The results from water quality testing provides some assurance that your private water supply was safe at the time of sampling. However, the quality of your water may change at different times throughout the year e.g. after heavy rainfall.


EHT&C can assist in water services consultancy.  We can cover the folloing areas:-

  • Private Water Supply Advice

  • Bathing Water Qulaity

  • Advice regarding potable water and commerical supplies

  • Legionella nad its control

  • Water based sysytems

  • Water smapling and result interpretation

Please call EHT&C on 0800 689 3512 for further information.

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