Guidance documents

Buying a dwelling with a Private Water Supply – What do I need to know?

This document is for prospective buyers of properties/homes, which receive a supply of water for domestic purposes from a private water supply. Domestic purposes includes drinking, washing/bathing and showering, washing of laundry, toilet flushing and central heating.

What should prospective buyers do?

Prospective buyers of property are advised to check the property deeds to familiarise themselves with any possible legally binding agreements with other parties concerning the responsibility for the control and maintenance of the supply. Buyers should seek legal advice in their interpretation and/or potential owner liability should any water quality issue arise or in the event of the supply becoming insufficient. Once a property with a private water supply (for domestic purposes) is purchased, the owner will become a “relevant person,” by virtue of one or more of the definitions specified in Section 80 of The Water Industry Act 1991. See The implications of this can be found here: If the water from a private water supply becomes, or is likely to become insufficient or unwholesome, a relevant person may be served a notice by the local authority to compel them to mitigate the risk caused by the unwholesome water or insufficient supply, in accordance with Section 80 of The Water Industry Act 1991. Where a supply is deemed a potential, or actual, danger to human health by the local authority a relevant person is liable to being served a notice in accordance with Regulation 18 (20 in Wales) of the respective private water supplies regulations by the local authority to ensure appropriate action is taken to mitigate this risk.

What questions should prospective buyers ask?

The following is a list of questions a purchaser of property supplied by a private water supply should seek answers for. These are suggestions that may be put to the vendor of the property (through a solicitor or estate agent), or a local authority who regulate private water supplies, to establish whether or not the water quality meets the required water quality standards and any future cost liability

Q: Has a risk assessment already been carried out by the Local Authority, and if so when, and what was the outcome?
Q: Did the local authority advise improvement works were required?
Q: If improvement works were required, have the risks since been remediated?
Q: What were the results of any previous sampling by the Local Authority?
Q: Did any results indicate a water quality problem and/or risk to health?
Q: Is there any water treatment within the property such as filters or UV disinfection units?
Q: Is the treatment appropriate and effective (you could ask the current owner for evidence that the system was fitted by a reputable and competent installer).
Q: Is the system compliant with Regulation 5 of the regulations?
Q: Is the UV system (where applicable) designed for use on drinking water supplies and sized appropriately?
Q: Has the current owner any maintenance logs or records for the supply?
Q: Have there been any water quality issues with the supply such as taste and odour, discolouration/appearance or insufficiency.
Q: Are there any documented instructions detailing the procedures should any problems with the supply arise, e.g. sufficiency or water quality such as taste or odour issues. These should contain telephone numbers or other contact details to arrange for alternative supplies, pipe repairs, treatment system maintenance etc.
Q: Is there a schematic/diagram of the supply showing the layout of pipes, tanks, inspection chambers etc. available?
Q: Is there a plan of the various parts of the treatment system, stating what each part is, for example any filters, iron or manganese removal systems, and disinfection?

Do I need a risk assessment?

Any private water supply used for domestic purposes that supplies two or more dwellings and/or other properties must be risk assessed every 5 years, and regularly tested in accordance with the regulatory requirements by the local authority. The frequency of testing will depend on the supply type.

If a supply provides water for domestic purposes to only a single dwelling, then the regulations do not require a risk assessment or testing unless:

In the absence of any risk assessment and or test results the quality of water on any prospective new dwelling or other property served by these types of supplies may be unknown and potentially not of the required regulatory standard, and/or a risk to human health. Prospective buyers are recommended to request a risk assessment and testing by the local authority. This will give an indication of the quality of the supply, as well as highlighting any areas of concern that may require remediation, as well as any ongoing costs expenditure. It should be noted that there is a fee for any risk assessment or sampling carried out on request. However where a local authority has concerns that a supply to a single domestic dwelling is a risk to human health, the regulations require the local authority to investigate, which may require the collection of samples and/or a risk assessment to be carried out. Under these circumstances no charge is made.

Where a supply serves multiple dwellings/properties the local authority will only collect one sample per supply for analysis on each visit (they are not required to take samples from every property on the supply each time). Where a dwelling is part of a community of properties served by a supply, the local authority may sample on a rotational basis, or where they consider the risk to be greatest. The Regulations allow the local authority to recover these costs. Charging rates for local authority private water supply activities should be available on their respective websites and can usually be found by searching for “private water supplies” in their website.

October 2018