Regulation 31 (Reg31)

Regulation 31 (Reg31) approval is required for products and materials used in contact with public drinking water supplies in England and Wales.

With direct experience supporting Reg31 submissions, AquaCompliance provides structured guidance in navigating DWI approval processes.

Working between manufacturers, laboratories and regulators, we ensure requirements are aligned ahead of submission and effectively managed throughout testing and review. This approach helps reduce delays, minimise rework and support right-first-time outcomes.

What is Regulation 31?

Regulation 31 is governed by the Drinking Water Inspectorate (DWI) and applies to products and materials used in contact with potable water within public supply systems.

Approval is required to demonstrate that products do not adversely affect water quality or pose a risk to public health.

The level of testing required depends on factors such as material / product type, application and contact conditions.

Where Regulation 31 Applies

Reg31 typically applies where products or materials are introduced into public water supply systems and may come into direct or indirect contact with potable water.

This commonly includes:

  • Components used within public water supply infrastructure
  • Materials used in treatment, storage or distribution
  • Site-applied and repair products (e.g. coatings and lining systems) requiring assessment
  • Products requiring assessment through laboratory testing, as determined by the DWI or relevant regulatory authority

Early clarity on applicability is critical, particularly where testing procedures, setup and approval requirements are defined by appointed laboratories and regulators.

Regulation 31 Application Process

Reg31 applications are submitted via the Drinking Water Inspectorate (DWI) online portal and require completion of structured application forms aligned to specific product or material categories.

Each application requires completion of multiple sections, supported by technical documentation including material formulations, Instructions for Use (IFU), technical data sheets (TDS), bill of materials (wetted parts) and relevant safety documentation. The level of detail and structure of this information plays a key role in how requirements are defined and assessed.

Once submitted, applications are reviewed by the DWI and assigned a reference number. During the review process, queries or requests for additional information may be raised at any stage and must be addressed before approval can be granted. Testing requirements are defined by the DWI and are typically formalised through a Test Requirements Letter (TRL) issued during the review process.

Responsibility for the application remains with the applicant, even where a consultant is engaged.

How AquaCompliance Supports

AquaCompliance supports manufacturers through a structured, delivery-focused approach, managing requirements from initial assessment through to approval.

  • Regulatory Pathway Definition — Clarifying how Reg31 applies and identifying the appropriate application route based on product type, application and market.
  • Documentation Review — Assessing available technical information and supporting data to identify gaps prior to submission.
  • Laboratory Coordination — Liaising with accredited laboratories to align capability, capacity, timelines and submission readiness.
  • Regulatory Engagement — Supporting communication with regulators and stakeholders to ensure queries are addressed and actioned efficiently.
  • Commercial & Technical Alignment — Identifying overlap across materials, products and approvals to streamline testing strategies, reduce duplication and manage overall project cost.
  • Application & Project Management — Coordinating activities from submission through to approval, including ongoing management of applications within the DWI portal

Key Considerations

Reg31 approval is influenced by several factors that should be considered early to avoid delays and rework:

  • Defining the correct approval route based on product type and application
  • Alignment between material testing and final product approval requirements
  • Availability and suitability of existing technical data and test reports
  • Laboratory capability, capacity and lead times
  • Clarity of requirements defined by the DWI and designated laboratory
  • Continuous and coordinated communication between internal teams, laboratories and regulatory stakeholders
Additional factors can significantly influence testing scope, timelines and overall project cost:
  • Material composition and formulation — A key factor influencing testing scope, including any necessary method development requirements
  • Supply chain complexity — Including multiple material and component suppliers, which can increase coordination requirements, expand testing scope, overall project cost and timelines.
  • Opportunities to leverage existing data — Existing approvals or test data may reduce duplication and support more efficient project delivery
  • Gaps in documentation or material data — May require additional testing or clarification
  • Alignment of documentation across standards — Where accepted by regulatory bodies, this can support efficiency and reduce rework

Testing requirements are typically defined during the project and may involve specific methodologies, product configurations or dedicated test setups. These factors can influence laboratory availability, timelines and overall project cost.

Early clarity across these areas supports project delivery and helps maintain alignment from initial submission through to approval.

Related Requirements

Regulation 31 (Reg31) approval forms part of the UK regulatory framework and may sit alongside other requirements depending on product type and application.

Within the UK, this may include:

Regulation 31 operates as an independent approval pathway; however, aligning it with related UK requirements supports right-first-time project delivery.

The technical data, material assessments and supporting documentation developed through Reg31 projects can be structured to support wider global compliance programmes, enabling more efficient planning across multiple approval routes.

While international frameworks such as the EU Drinking Water Directive (DWD) / MHR and North American standards (NSF/ANSI 61 & 372) are not directly interchangeable, a coordinated, multi-standard approach enables better use of existing data and more effective alignment of testing and documentation strategies.

If you are planning a new application, reapproval or product change, early clarity on requirements and approach can significantly improve timelines and outcomes.

AquaCompliance supports projects from initial assessment through to submission and approval, helping to ensure alignment, maintain progress and deliver with confidence.

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