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Materials in contact with drinking water (Regulation 31)

Regulation 31 prohibits a water company from applying any substance or product to, or introduce any substance or product into, water which may impact drinking water quality. This covers all chemicals, construction and treatment products used by water undertakers, from the source of the water, up to the point of delivery to the consumer’s building. This is a critical duty because materials can taint water by taste, odour or by leaching of harmful substances. The regulation sets out how approvals can be given to construction and treatment products and materials that do not prejudice water quality and ultimately consumer safety. 

During 2024, the Inspectorate continued to receive and process applications for approval of products in contact with drinking water (under regulation 31). The volume of applications received was:  

YearTotal applicationsNew applicationsProduct changesProduct reapprovals
2024177477951
2023126246142
2022145326251
2021146236260
Table 42 – Regulation 31 applications, changes and reapprovals

The Inspectorate has continued working with its IT partners to further develop the regulation 31 portal for product approvals. The system has replaced the previously used manual application forms with online, interactive application forms that will guide applicants in providing all the necessary information for an approval or product change to be considered. The online process will have the benefit of meeting accessibility standards, making them available to more people with the next phase of the project delivering and end to end process and approved products list transformed from a monthly, published PDF document to an interactive, searchable website which is updated in real-time. This will effectively become a live, online catalogue of approved products.  

A significant increase in poor product stewardship was seen in 2024 with approved products being revoked from the Secretary of States List with immediate effect and a notification letter of prohibition issued for the use of a product with an unauthorised name change. Subsequent investigations led to further revocations in early 2025. All issues identified were as a result of unauthorised changes being made.

In December 2024 a revocation was applied to Puriton Pipes (DWI 56/4/1112) manufactured by Radius Systems Ltd. The company had made a late submission for the reapproval and once all the relevant documents were submitted, the reapproval was granted. Subsequently however, the Inspectorate was informed that the information provided was incorrect and that unauthorised changes had been made to the product. This resulted in the immediate revocation of the product and extensive liaison with the company. The water industry was informed of the revocation via a regulation 31 information letter (ref: R31-03/2024)

A Notification Letter (ref R31-01/2024) was issued to the industry following an unauthorised name change to an approved product which prohibited its use. As part of a rebranding process, MBCC provided suppliers with products labelled with a handwritten label stating the new Sika product name, Sikadur-CombiFlex 930 with Sikadur-CombiFlex 933 (DWI 56/4/1569), and this was accompanied by the MBCC IFU document for MasterSeal 930 joint bandage with MasterSeal 933 adhesive (DWI 56/4/144). The product name and the details on the IFU should be identical. This was initially identified by Northumbrian Water who notified the regulation 31 team. This was subsequently found to be a widespread issue.  

The company had not completed the change process for this product which resulted in several companies having to remove the product from assets where it had been applied, with other companies forced to keep assets out of supply until the process had been completed and the name change authorised. This resulted in a significant number of meetings with water company representatives and the manufacturer to rectify the issue during what was an already busy period for the team.

This was yet another example of both poor product stewardship by the manufacturers and complacency on behalf of water companies and contractors who failed to identify that the IFU did not match the label on the product container, and the product name did not appear on the List of Approved Products. As a result, water companies were requested to notify use of this product to the Inspectorate as an event.

The Inspectorate does not take the decision to revoke products or prohibit the use of products lightly, however, where the stringent requirements to maintain the product approvals are not met, and constitutes a potential concern to public health, this threshold is met.

In addition, a large number of approval holders either made late applications or omitted to apply for product reapprovals which resulted in a delay in reapprovals being assessed and an increase in expired products with manufacturers having to undertake the entire process of product approval from the beginning.

These incidents were extremely time consuming for the small regulation 31 team to manage and impacted the growing back log of applications. A decision was taken to prioritise reapprovals during this time to ensure continuity of product availability.

A list of all products approved and under consideration under regulation 31 is available on the Drinking Water Inspectorate website:  https://www.dwi.gov.uk/drinking-water-products/resources-for-water-companies/approved-considered-products/

The team were also involved in the development of the new Materials in Contact awareness course being offered by EUSR and continue to work on various EN standards covering treatment chemicals, filter media and material leaching, biocides and radioactivity along with managing some research projects. We continue to receive large numbers of enquiries relating to Water Fittings regulations such as recirculating showers, grey water reuse and wider recycling schemes.

There has been significant work undertaken by the team to secure testing facilities for BS6920 and full regulation 31 testing throughout the year. We are also collaborating with the water industry to resolve the issue, and this work is ongoing. Laboratories are required to demonstrate and evidence compliance with the relevant standards to become designated for regulation 31 testing.

Anglian Water – Regulation 31 Case

At Northampton Magistrates court on15 May 2025, Anglian Water was fined a record £1.42 million following a prosecution by the Drinking Water Inspectorate for drinking water failures affecting around 1.3 million people. 

Between June and December 2021, Anglian Water notified the Inspectorate of four water quality events where unapproved pipework and material was used in several tanks in the supply of drinking water.

Anglian Water pleaded guilty to five offences under regulation 33 by virtue of failure to comply with regulation 31(1) of the Water Supply (Water Quality) Regulations 2016 (as amended) for repeatedly introducing non-compliant materials into the water supply. The investigation identified compelling and credible evidence for the following failures and findings at four separate sites.

Issues common to each event 

The investigation identified compelling and credible evidence for the failures and findings below (common to all 4 schemes):  

  • Lack of control of the regulation 31 process to prevent the installation of unapproved products in a submerged environment repeatedly (strong evidence pointing to failure to control products used, backed with witness statements, contractor witness statements, photographs and Materials in Contact records)  
  • Poor management of contractors and supply chain/procurement arrangements (backed by witness statements, procurement and delivery records)  
  • Lack of regulation 31 training in place at the time of installation for engineers, water quality, or project managers (training records, witness statements)  
  • The coating of the pipes (in all events) deteriorated to a powder/flakes that was easily removed from the surface of the pipes. The analysis of the coatings contained controlled phthalate-based substances, some of which are banned from children’s toys, cause birth defects and cancers (evidence includes compound analysis reports, SNARLS, pictures, and witness statements). 
  • Water quality monitoring did not detect a deterioration in quality (except at Kedington works (see below),  – however not all relevant parameters were analysed regularly and consistently (evidence included sampling records).
  • At Kedington works, Anglian Water detected a taste described as “sweet” by two laboratory analysts, from a sample of the unblended treated water on 11 May 2020. This is an unusual taste for drinking water and could have been as a result of paint particles, subsequently shown to contain xylene, impacting on the quality of the water being supplied.

Approximately 1.3 million customers across the Anglian Water region have been impacted by these failures. The Inspectorate was critical of the wrong products being used in submerged environments, lack of controls and of the company’s management of products. The Inspectorate was also critical that an asset remained in service after it had been identified that non-approved products were being used.  

Failure to control the installation of unknown and untested materials can have consequences; this prosecution serves as a reminder that drinking water must come first as a service. 

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