Private Water Supplies

Due to the geographic nature of the island environments across the Isles of Scilly, there are some properties that cannot easily connect to the mains supply and a private supply is the only option for water.  In other cases, the availability of groundwater offers choice and can be seen as a cost- effective way to obtain water. A private water supply is defined as one which is not provided by a water company, such as South West Water. The majority of the private water supplies across the islands are sourced from boreholes and wells.

In April 2020, the monitoring and management of all private water supplies was transferred under new regulations to the Council of the Isles of Scilly. This means that trained and authorised officers from the cios environmental health team will manage the quality of private water supplies across the islands, ensuring the water is safe, enabling the council and supply users to meet their legal responsibilities. The regulations require officers to risk assess and sample private water supplies when legally required or when requested. Risk assessments are initially undertaken to identify any vulnerability in the supply before any further action is taken. Officers are also able to advise on how best to protect a water supply from contamination. All water samples taken will be analysed by a ukas accredited laboratory which works to internationally agreed standards. Any supplies found to fail the water quality standards will need remedial intervention to ensure the water is safe to consume.

Tell us about your supply

Local authorities are required to keep records of all the private water supplies in their area and to send information about these supplies to the drinking water inspectorate annually. To register a private water supply, please download the  registration questionairre document to the right:

Once completed the form can be submitted; by email to: or post to: Environmental Health, Town Hall, St Marys, Isles of Scilly, TR21 0LW

You can also use this form at any time to tell us about a new private water supply or to provide information about an existing supply such as a change of use or new contact details.

Please view our privacy notice to find out more about how we use the information collected relating to private water supplies and personal data.

Private water supply uses

The majority of the islands private water supplies are used for human consumption. Private water supplies can also be used for purely domestic purposes such as cooking and washing, or for large scale commercial operations such as farming or breweries.

Ensuring clean, safe drinking water is the biggest concern and this can be achieved in several ways including protecting the source and the maintenance of secondary treatment, such as filtration and disinfection.

Private water supplies regulations and fees

Private water supplies are regulated by national legislation – the water industry act 1991 and the private water supplies (england) regulations 2016 (as amended) and the private water supplies (england)(amendments)2018.

The private water supplies regulations require that all water intended for human consumption must be wholesome and must not constitute a danger to human health.

Section 77 of the water industry act 1991 requires a local authority to keep itself informed about the wholesomeness and sufficiency of every private water supply within its area. Each local authority achieves this by conducting its statutory duties which includes; risk assessments, investigations, authorisations and monitoring (sampling and analysis).

The private water supplies regulations 2016 require local authorities to carry out monitoring of all supplies, except those which serve only one domestic property (monitoring can be undertaken on request).

The regulations also make provisions for local authorities to charge fees to the relevant person(s) for conducting these duties. The following leaflets explain further the importance of safe private water supplies and the regulatory service provide by the council of the isles of scilly. The pws charge scheme can be found in the download section to the right of this page.

  1. Private water supplies – be safe
  2. Private water supplies – a regulatory service

Keeping your water supply safe

There are many things you can do to keep your water supply safe. Contamination from a variety of sources can occur potentially at any point throughout a water supply system if it is not robust and adequately protected. The drinking water inspectorate have produced a leaflet outlining the measures you can take to prevent and remediate the main forms of contamination that pose a risk to a private water supply.

The following links can provide further information on all aspects of private water supplies.

The drinking water inspectorate -

Users of a private water supply -

Consumer information -     

Please contact  environmental health for further information and advice by emailing   or phone 0300 1234 105.


Our environmental health service privacy notice, which details how we use the information collected relating to private water supplies and personal data, can be viewed at the following link: