Drinking Water
Wales 2025

Public supply statistics

Set out in this report are the key facts about the quality of the public water supplies in Wales, which is served by 3 water companies delivering supplies to 3.31 million consumers

Compliance with the Regulations

Compliance with the drinking water standards is consistently high in Wales. Testing is designed to verify drinking water quality at practicable intervals at key supply system locations.

Private water supplies

Under the Regulations, drinking water should be 'wholesome' meaning it does not contain any microorganism, parasite or substance at a concentration or value that exceeds limit values or would constitute a potential danger to human health. 941 of 23,939 tests reported by the local authorities in Wales in 2025 failed to meet one or more of the standards for wholesomeness.

Compliance Risk Index

Compliance with the drinking water standards is consistently high in Wales. Testing is designed to verify drinking water quality at practicable intervals at key supply system locations. The Inspectorate uses the CRI to measure the impact of a compliance failure on company performance, and the potential impact of those compliance failures on consumers.

Lead in water

The source of lead in drinking water is mainly communication pipes owned by water companies and supply pipes owned by consumers within their property which are made from lead. The Inspectorate wishes to work more closely with the industry lead steering group to increase the quality of data captured during failure investigations.

Events reported to the Inspectorate

Water companies are required to notify the Inspectorate of any event which, by its nature has, or is likely to, adversely affect the quality or sufficiency of the water supplied to consumers.

Event Risk Index

The DWI use the Event Risk Index (ERI), which measures the impact of any events and the potential consequence on consumers as well as understanding the actions taken by the company in response. The ERI is designed primarily for the purposes of effective regulation, ensuring appropriate scrutiny is directed to those areas of greatest relative risk.

Service reservoirs

There were 3 water quality events attributable directly to poor asset health, including 2 microbiological contamination events at reservoirs and 1 microbiological contamination event at a treatment works.

Audits in the reporting year

The Inspectorate undertakes an annual programme of technical audits to provide independent assurance that water companies are effectively managing risks to drinking water quality. These audits form a key part of regulatory oversight and enable the Inspectorate to examine how companies design, operate and maintain their systems to protect public health.

Air valves audit - Industry wide

The Inspectorate undertook an industry wide programme of technical audits focused on the management of air valves across water companies in England and Wales.

Bottled water storage audit - Industry wide

The Inspectorate audited several bottled water storage and distribution facilities, as well as company procedures for deploying bottled water during incidents

Microbiology breach

Microbiological compliance breaches in Wales continued to highlight weaknesses in service reservoir integrity, asset resilience and investigation processes. Several E. coli and coliform detections were linked to structural defects and water ingress, while resilience limitations frequently delayed inspections and root cause investigations.

Discolouration

The performance of the Welsh water companies remains below the industry average, with little evidence of improvement over the reporting period. While the wider sector has demonstrated progress in several areas, performance across Wales has remained broadly unchanged, indicating a continued need for targeted action to address underlying challenges and drive measurable improvements.

Recommendations to water companies

Recommendations are the Inspectorates primary method for undertaking enforcement action. They are issued to water companies when the Inspectorate identifies a failure to meet the statutory requirements of the Water Supply (Water Quality) Regulations 2016, or when the Inspectorate identifies a risk to public health.

Recommendations Risk Index

RRI measures all companies’ performance in recommendations against the industry. Recommendations are the first level of regulatory intervention. Regression analysis can be seen as the central black line. A position below this line means a company is receiving fewer recommendations and/or lower scores attached to those recommendations than would be expected.

Consumer contacts

The acceptability of drinking water is ranked by consumers as their top priority and can be affected by several factors including its appearance, for example, discolouration or aeration, or the taste and/or odour.

Individual PFAS in drinking water

PFAS are a group of manmade compounds, the basis of which are chains of carbon and fluorine atoms. They contain at least one fully fluorinated methyl or methylene group. The carbon-fluorine bond is very strong and so these compounds do not degrade easily in the environment.

Enforcement action

The Inspectorate has a range of enforcement powers which we utilise to compel companies to ensure that drinking water is of the highest quality and the systems in place to ensure its quantity and quality are sufficiently resilient.

Materials in contact - Regulation 31

Regulation 31 prevents water companies from using substances that could affect drinking water quality, including chemicals and construction products from source to delivery.

Inspectorate workload

As well as undertaking its regulatory duties the Inspectorate receives a large number of enquiries, complaints and data requests each year. There has been an exponential increase in the number of enquiries received by the Inspectorate over the last 5 years.

Priority considerations