Version 6.5, April 2021


1. Introduction

This Advice Sheet outlines the regulatory requirements for treatment chemicals, filtration media, ion exchange resins and on site electro-chemical generating processes used in the treatment of water intended for human consumption.

2. Treatment Chemicals and Filter Media

2.1 Chemicals and Media covered by European Standards

Many commonly used treatment chemicals and filter media are now covered by European Standards which are published in the UK by the British Standards Institution (B S i) as a British adoption of a European (E N) standard (BS E N s). Where an appropriate European Standard exists for a treatment chemical the water undertakers are obliged to purchase these products by reference to that standard. It is the water companies’ responsibility to ensure that the treatment chemicals they use conform to the standard, either by reference to the conformity statements provided by the supplier or by their own checks.

Where a European Standard exists member states are not permitted to have their own approvals. However, a member state can impose conditions of use on a chemical or media on the grounds of justifiable additional technical requirements, e.g. protection of public health. In the UK conditions of use are set for a number of treatment chemicals and these are published in the List of Approved Products. Water companies must comply with the conditions of use stated in the List.

Where chemicals conforming to European Standards are mixed before being sold the resultant mixture is not considered to conform to a European Standard and approval from the Authorities must be obtained before the product is used in public water supplies (see below).

2.2 Treatment Chemicals and conformity to the Biocides Regulations (GB BPR)

Products that claim biocidal effects, such as disinfectants, may require authorisation under the Biocidal Products Regulation (GB BPR) in addition to meeting the provisions of regulation 31. The two provisions, G B B P R and Regulation 31, are operated separately. Products approved under the GB BPR may not be suitable for approval under Regulation 31.

It is up to the end user or the manufacturer/supplier of a product to check that it conforms with all the appropriate regulations. Product approval holders should check whether their product is covered under the GB BPR and if so should ensure that the active substance(s) in their biocidal products are:

  • under review for that the relevant product type and their active substance supplier is listed in accordance with Article 95 of the GB BPR; or already approved for the relevant product type or listed in Annex I of the GB BPR (simplified actives list);
  • and that they have made any necessary application for Product Authorisation under the GB BPR.

Information on the GB BPR, including how to check the status of an active substance, how and when to apply for product authorisation and what actions need to be taken whilst an active substance is still under review, is available on the Health and Safety Executive website at . Any queries about the applicability of the GB BPR should be addressed to

2.3 Approval of Chemicals and Filter Media

Where a chemical or filter media is not the subject of a British adoption of a European (E N) standard (B S E N s), or a combination of a mix of BS ENs, an application should be made using the “chemicals” or “filter media” application forms, on the DWI Reg31 applications portal.

3. Ion Exchange Resins

Ion exchange resins, including those used in the preparation of water for use with treatments chemicals are not the subject of any B S E N standards and require approval under the regulations, including those used to produce any diluent used in combination with any treatment chemical that is dosed into the water supply. Applications for approval of ion exchange resins should be made using the filter media application form, on the DWI Reg31 applications portal.

Please ensure that you submit the following product information with your application.

Product description

  • the type of resin;
  • the media bed size, capacity etc.;
  • operational flow rate;
  • empty bed contact time;
  • regenerant used and volume;
  • rinse water volume;
  • pH values attained and how attained (including any acid or alkali used).

Description of the manufacturing process

  • This does not need to be a detailed manufacturing protocol but should give details of raw materials used, the temperature of each part of the manufacturing process and the products of each part of the manufacturing process. It is important to give details of any materials that are not entirely consumed during manufacturing.


  • Full details on how the ion exchange resin will be regenerated, including how it is ensured that regeneration chemicals are adequately removed before the resin is returned to service.

Instructions for use (IFU)

  • This should meet the appropriate requirements set out in Advice Sheet 2 ;

4. Products for Generating chemicals On-Site

All chemicals generated on-site should meet the appropriate national standard, as detailed in the List of Approved Products, Annex 2. For chemicals that do not meet the appropriate national standard or a national standard does not exist then approval is required for the chemical generated.

Applications for approval of products for generating chemicals on-site should be made using the Electrochemical generating process application form, on the DWI Reg31 applications portal.

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