Risk Assessment tools and tips


This page provides the tools to assist risk assessments of private supplies. For general guidance on the requirement to risk assess see the information notes here.

Conducting a risk assessment

The Inspectorate has developed a number of risk assessment tools to assist local authorities in undertaking risk assessments for private water supplies as required by regulation 6 of The PWS regulations 2016. These tools can also be used for supplies to single domestic dwellings where a risk assessment has been requested.

In response to requests from local authorities for a condensed version of the risk assessment tool for use on simple systems with common types of treatment, there is also an edited version of the tool. This is listed as ‘risk assessment lite’ and may be typically used on supplies that consist of a single source followed by one or two stages of treatment, such as prefiltration and UV disinfection.

Please ensure you use the most up to date version of the risk assessment tool. The version number can be found on the first tab in each tool. All tools should be compatible with Excel 2010 onwards. Please contact the Inspectorate should you experience any compatibility issues.

Regulation 8 Supplies only

Risk Assessment Full Tool – Regulations 8, 9, and 10 (Regulation 11 in Wales)

Risk Assessment Lite – Regulations 8, 9, and 10 (Regulation 11 in Wales)

Risk Assessment tool for toilet flushing

Risk assessment for PWS that originate from mains water and are classed as Regulation 8 supplies only

Full site risk assessment suitable for all private supplies

Condensed from full site risk assessment, to be used on simpler sites. May be suitable for sites requiring reassessment.

Condensed risk assessment tool for private supplies that are used exclusively for toilet flushing

V2.06 (Excel 340KB)
Date of last update: 18/05/23

V3.08 (Excel 388KB)
Date of last update: 18/05/23

V2.11 (Excel 724KB)
Date of last update: 18/05/23

V2.05 (Excel 127KB)
Date of last update: 22/12/23

Please see guidance for RA Lite (PDF 752KB)

Please see guidance for RA Lite (PDF 752KB)

Explanatory Notes (PDF 752KB)
Date of last update 26/11/18

A training video is available on the online risk assessment tool.

These tools are produced under licence, permitting third parties to use the risk assessment tool by local authority agreement, and without altering, copying or using it for commercial gain. The tools are therefore provided in a protected format and we cannot supply them unprotected.

DWI has also produced an Action Plan look up table listing common mitigation measures.

Note on Poly and Perfluorinated Alkyl Substances in Drinking Water

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a group of man-made chemicals that include PFOA, PFOS and other related substances. They have been used widely for a range purposes from industrial to household products, that have had or continue to have widespread use in England and Wales. Certain PFAS compounds are known to have the potential to persist in the environment; including in water and some have shown the capability to bioaccumulate. This has raised a keen interest in better understanding their potential impact on the environment and toxicity.

When considering the sources of PFAS in drinking water catchments, current research has found that they include:

  • Fire stations and training sites.
  • pollution incident sites.
  • Mechanics.
  • Air transport sites.
  • Military bases.
  • Chrome plating sites.
  • Carpet, leather, paper and textile manufacturing.
  • Landfill sites.
  • Waste water treatment works.

However, detectable concentrations of PFAS have been found in water where there is no apparent connection to any of these. As such, local authorities should also consider the risk of unknown sources of PFAS in private supplies, where the potential for their presence may exist. Where they are found, due to their persistence and mobility in the environment, the potential area and number of supplies that could be affected, should be considered.

The Inspectorate has commissioned research into the analysis and treatment of PFAS in drinking water.  This website will provide updates when more information is available, so please keep checking.

Without being able to assess the suitability of treatment, local authorities will be reliant on sample results to inform their risk assessments. At present, there is a limited capacity at laboratories for the analysis of PFAS. Local authorities should consult with laboratories to establish when there may opportunity for PFAS analysis. In the first instance, it is important for local authorities to understand if any of their supplies are at high risk of the presence of PFAS. High risk supplies can then be prioritised for further action which may include sampling and analysis when it is available. Sources of data and information to help inform risk assessments include the Environment Agency, and local water companies, who are undertaking sampling and analysis of various environmental waters.

Various agencies have commissioned research into the toxicology of PFAS. Local authorities should consult their UK Health Security Agency (UKHSA) or Public Health Wales for more information on PFAS in water used for domestic purposes, particularly where analysis confirms their presence, as health advice will be informed by the specific substance/s found, and their concentrations. It may be necessary for local authorities to keep an open dialogue with UKHSA or Public Health Wales on PFAS.

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