When a product is approved for use with drinking water, that should mean the compliance box is ticked. Right?

Not quite.

Regulation 31 compliance is not simply a matter of finding a product name on an approved list. The exact product must be suitable for the proposed use, its approval must still be valid, and every relevant condition and Instruction for Use must be followed. Compatibility, application, curing, commissioning and record keeping can all matter too.

That makes Regulation 31 relevant far beyond water quality teams. Designers, engineers, buyers, project managers, site supervisors, contractors and consultants can all make decisions that affect whether a product is used compliantly.

The key point: An approval is not a blanket permission to use a product anywhere, in any way or alongside any other approved material.

What is Regulation 31?

Regulation 31 of the Water Supply (Water Quality) Regulations 2016 (as amended) controls the application and introduction of substances and products used by public water suppliers in England. Its purpose is to prevent chemicals, construction products and treatment materials from compromising water quality or consumer safety.

The scope runs through the public water supply system, from the source of the water to the point of delivery at a consumer's building. Equivalent requirements apply across the rest of the UK.

Note: The detail differs between nations. Organisations should check the current legislation and regulator guidance for the location in which work is being carried out.

Why products in contact with drinking water need control

Materials do not have to cause an obvious contamination incident to create a problem. An unsuitable or incorrectly used product may affect the taste, smell or appearance of water, encourage microbial growth, or allow substances to leach into the supply.

The Drinking Water Inspectorate reported that 99.97% of regulatory samples from public water supplies in England met the required standards in 2025. That is reassuring, but high standards are maintained through consistent control. The Inspectorate was also notified of 586 water quality events during the year. Those events had many causes and were not all related to Regulation 31, but they underline why the industry cannot become complacent.

Who is responsible for Regulation 31 compliance?

The legal duty in England sits with the water undertaker or relevant licensee. In practice, however, compliance can be secured or lost through decisions made across a project and its supply chain.

Regulation 31 awareness is therefore relevant to people involved in:

• Design and specification. selecting products, materials, components and treatment processes for water assets
• Procurement and supply. checking the exact product, approval status, manufacturer, documentation and any substitutions
• Installation and application. following preparation, mixing, environmental, curing and commissioning requirements
• Supervision and assurance. confirming work is completed as specified and that deviations are escalated before an asset enters supply
• Handover and record keeping. retaining approvals, Instructions for Use, test results, advice and evidence of compliant use

What types of products can fall within Regulation 31?

The rules cover a broad range of chemicals, construction products and treatment materials used in the public water supply. Depending on the product and how it is used, this can include:

Why appearing on the approved list is not enough

The Drinking Water Inspectorate's live List of Approved Products is an essential reference, but it must be used properly. Before specifying, purchasing or using a product, teams should ask more than one question.

• Is it the exact product? Check the product name, manufacturer, approval reference and any other identifying details. A similar name or related product is not automatically covered.
• Is the approval current? Approvals can expire, be modified or be revoked. Check the current live list rather than relying on an old download or historic project record.
• What are the conditions of approval? The list may restrict where, how or under what circumstances a product can be used.
• Do you have the approved Instruction for Use? The IFU forms an integral part of the approval. It can cover storage, preparation, mixing, application, curing, disinfection, commissioning, testing, maintenance and disposal.
• Is it suitable for the substrate and surrounding products? Two products may each be approved individually without being approved for the proposed combined use.
• Has anything changed? Changes to formulation, raw material source, manufacturing process, location, product designation or approval holder can affect the approval.
• Can you evidence the decision? Keep a clear record of the product checked, approval and IFU version, technical advice, method of application, test results, deviations and final acceptance.

A 2026 case that shows the difference

A confirmed provisional enforcement order published by the Drinking Water Inspectorate in March 2026 provides a clear example. It concerned a section of strategic pipeline between Waddington, south of Lincoln, and Harrow, east of Grantham.

The pipe and the repair product both held Regulation 31 approval. However, the Inspectorate stated that they had not been approved for use together in the manner applied and that the use was contrary to the manufacturer's Instructions for Use and the conditions of approval.

The order prohibited the supply of drinking water through the affected 25.1 km section until compliance could be demonstrated. The required evidence included a list of products and materials in contact with the water, application methods, curing details and testing.

The lesson: The question is not only 'Is this product approved?' It is 'Is this exact use of this exact product compliant with the approval, the IFU and every relevant condition?'

The consequences can go well beyond paperwork

In May 2025, Anglian Water was fined £1.42 million following a Drinking Water Inspectorate prosecution relating to unapproved coatings used on pipework submerged in drinking water tanks. The Inspectorate said its investigation also found weaknesses in staff training and oversight of contractors and the supply chain.

Regulation 31 failures can lead to assets being kept out of supply, materials being removed, additional testing, delays, investigation, enforcement, prosecution and reputational damage. More importantly, they can create risks to water quality and public confidence.

A practical Regulation 31 check at every stage

Common Regulation 31 misconceptions

'It is approved, so we can use it anywhere': False. Approval is tied to defined conditions and the accepted Instruction for Use.

'WRAS approval is the same as Regulation 31 approval': False. Water Fittings approvals primarily concern products used within premises, while Regulation 31 covers the public water supply from source to the point of delivery. BS 6920 test results may support an application, but they are not automatically a Regulation 31 approval.

'It is only a small component, so it does not matter': Not necessarily. Regulation 31 includes a route for some small-surface-area products, but the water supplier must make and evidence the appropriate assessment.

'This is only for water quality specialists': False. Specification, procurement, installation and handover decisions can all affect compliance.

'Training replaces technical advice': False. Awareness training supports better decisions, but product-specific approval conditions, manufacturer instructions and competent technical advice still have to be followed.

Why Regulation 31 is under greater scrutiny

The Government's 2026 water White Paper, A New Vision for Water, says drinking water standards cannot be taken for granted. It proposes more regular review of drinking water regulations, stronger scientific and public health input, improved testing capability and a more proactive regulatory system.

These are proposals for wider reform, not a reason to wait. Regulation 31 duties already apply, and recent enforcement shows that product governance, workforce awareness and evidence need attention now.

Build Regulation 31 awareness across your team

The EUSR Products for Drinking Water course helps operatives, supervisors, managers and professionals understand how the relevant regulations apply in practice.

Developed with UK water companies and industry stakeholders, the half-day programme covers:

• the scope and applicability of the regulations, and the consequences of non-compliance
• the regulators' List of Approved Products for Drinking Water
• Instructions for Use and conditions attached to a product
• small-surface-area products and water treatment chemicals
• specific regulatory requirements, seeking advice and record keeping
• Delegates complete a 25-question multiple-choice assessment set by EUSR. Successful completion results in an EUSR registration valid for three years.

Ready to strengthen Regulation 31 awareness across your workforce? View the EUSR Products for Drinking Water course or call Essential Site Skills on 0115 8970 529 to discuss group training.

Frequently asked questions

Is EUSR Products for Drinking Water training legally mandatory?

Regulation 31 does not name a particular training certificate. The EUSR scheme is designed to build awareness and provide a consistent, independently registered record of successful training and assessment. Employers, water companies, projects or contracts may set their own competence and training requirements, so these should also be checked.

How long is the EUSR Products for Drinking Water registration valid?

Registration is valid for three years. To renew, the individual must repeat the training and assessment with an EUSR Approved Trainer.

Does an approved product remain approved indefinitely?

Not necessarily. Approvals may expire, be modified or be revoked. The current DWI list and the applicable conditions should be checked each time a product is specified or used.

Can two approved products always be used together?

No. Each product's conditions and Instruction for Use must support the proposed combined use. The 2026 pipeline enforcement order demonstrates why this check matters.

Who should attend the course?

It is suitable for operatives, supervisors, managers and professionals involved in operations, developer services, capital delivery, procurement, consultancy and supply-chain activities connected with drinking water.

Important: This article provides general awareness information. Always check the current legislation, regulator guidance, product approval and Instruction for Use, and seek competent advice for the specific application.