DWI UK Regulation 31 Approval Testing

Regulation 31 of the Water Supply (Water Quality) Regulations governs the approval of products and materials used in public drinking water systems in England and Wales. It is designed to ensure that any substance or product in contact with drinking water, from source to tap, does not compromise water quality or public health.

The regulation is enforced by the UK Drinking Water Inspectorate (DWI).

Once your product formulation and documentation are reviewed by the DWI, you’ll receive a Test Requirements Letter outlining the specific testing needed. Depending on the product, this may include:

• BS 6920 testing (materials in contact with drinking water)
• Leachate studies (required for many treatment chemicals and site-applied products)
• Specific analysis of determinants based on product composition and use
• GC-MS screening to identify organic substances
• Total Organic Carbon (TOC) analysis

Testing protocols vary by product type, such as coatings, membranes, resins, or site-applied materials, and follow relevant British Standards and DWI specifications.

Following testing, NSF prepares a comprehensive report formatted for submission to the DWI. This report supports DWI’s independent toxicological review and final approval decision.

Approvals are typically valid for five years, after which re-approval is required to maintain your product’s status. If your product formulation, suppliers, modifications, or manufacturing process change, you must inform the DWI. Depending on the nature of the change, additional testing and review may be required.

• Clearest path to approval – Results are delivered in a DWI-ready format, so you can add them directly into your application.
• One partner for all required testing – We are the only DWI-designated lab offering both BS 6920 and leachate studies in one place, removing the hassle of coordinating multiple labs for required test data.
• Trusted results – All testing is completed in-house at our laboratory (UKAS-approved and ISO/IEC 17025 accredited) by technical staff who are experienced in Regulation 31 requirements.
• Clear communication and dedicated support – A single point of contact keeps your project moving, answers questions quickly, and ensures you always have exactly what’s needed for submission.
• Global regulatory support – Outside the UK, we offer testing and certification support for many other approvals, for when you want to commercialise your product in multiple regions.