Version 8.0; 04/05/2023

 1. Introduction

This Advice Sheet deals with the approval system for substances and products used in contact with public water supplies in the UK. The relevant regulations for public drinking water suppliers concern the introduction of substances and products and processes for use in the treatment and provision of public water supplies. All public drinking water suppliers shall not apply or introduce any substance or product into public water supplies unless one of the requirements of this regulation is met. One of these requirements is the substance or product has been approved by the Authorities.

The DWI operates the approval system on behalf of the English and Welsh Authorities. DWI accept applications for approval of products used in contact with water intended for human consumption from abstraction to the point of delivery to premises. DWI cannot accept applications for products used solely in water systems within premises unless they conform to the requirements of a private water supply and cannot deal with enquiries on such products – applications and enquiries should be made in accordance with the Water Supply (Water Fittings) Regulations.

2. Scope of the Approval System

2.1 Treatment Chemicals and Associated Products

  1. Individual chemicals and media that conform to an appropriate BS EN standard do not require approval by the Authorities provided all specified national conditions of use are met. These conditions are set out in Annex 2 of the “List”. Applications for these will not be accepted unless used outside the normal scope of the standard.
  2. Applications are considered for those chemicals that are not covered by a published BS EN standard.
  3. Applications are considered for associated products, such as filtration and adsorption media, that are not covered by a published BS EN standard
  4. Applications for mixtures of chemicals (whether or not conforming to a relevant BS EN standard) are required.
  5. Disinfectants used in emergencies – see Advice Sheet 9 for further guidance.
  6. Disinfectants for continuous use– must be approved as a biocide by HSE before an application for approval with drinking water – further information can be found in Advice Sheet 3

2.2 Construction Products

All construction products used in contact with water for human construction shall meet the requirements of the relevant regulations.

  1. All construction products that have a small surface area in contact with water and are unlikely to have an adverse effect on water quality do not require approval and should conform to the requirements detailed in Advice Sheet 8
  2. Applications are considered for all other non-metallic construction products used in contact with water, in water treatment processes, water supply pipelines (including raw water pipelines) and drinking and raw water storage installations (see also Advice Sheet 7).
  3. Applications are considered for all other metallic construction products used in contact with water, in water treatment processes, water supply pipelines (including raw water pipelines) and drinking and raw water storage installations. Details of the requirements of metallic compositions can be found in Advice Sheet 5

The use of products and substances used for research purposes are covered in FAQ16

Any concerns regarding the scope and use of a product or substance and where it falls within the requirements of the relevant regulations, please contact the water company or

3. Applications for Approval

The DWI review applications on a first come first served basis that entail the following types of applications:

  1. New applications – continue with this Advice Sheet for further details
  2. Changes to approved products – see Advice Sheet 4
  3. Re-approval of approved products – see Advice Sheet 11

The application process is undertaken online through our portal. All applications shall be made using this format, which has minimum requirements before a submission can be made. A Gateway registration for use is required prior to starting the application process, all approval holders will already have these details.

3.1 General Requirements

An Application for Approval may be made by any person and must be submitted on the appropriate format by selecting the appropriate product category online ensuring all supplementary information is in English.

The following information is required for all applications as part of the application process:

  1. The product name must be a unique reference that does not infringe any registered trademark or have the same name(s) as any other product(s).
  2. The Instructions for Use (IFU) for the product, all the appropriate requirements are set out in Advice Sheet 2. Any approval given for the product will be subject to the application and use of the product as specified in this IFU. Poorly written or badly presented IFU documents are the major causes of delays in processing applications. A product will not be considered by DWI for approval under the relevant regulations without a satisfactory IFU, and usually DWI will not agree to the release of any appropriate test requirements until they are completely satisfied with the IFU.
  3. Evidence of product and/or all of its non-metallic components suitability for use in contact with drinking water. The DWI require either evidence of material or product listing under the Water Supply (Water Fittings) Regulations, or BS6920 test report issued within the last 5 years. Details of test laboratories are available on our website. Details of Water Supply (Water Fittings) compliant products and materials can also be found on our website. For other evidence of suitability please contact DWI. Suppliers of components may be able to supply copies of their BS6920 test report or compliance to the Water Supply (Water Fittings) regulations. DWI reserves the right to request additional BS6920 testing.

3.2 Supplier Co-operation

Applicants should ensure their suppliers are aware of their intention to apply for approval and gain their co-operation in advance, with the provision of confidential formulation information. This should be sent directly to the DWI or entered through the online portal. Some suppliers may not wish to provide this information and this may impact the approval (see confidentiality below). Always ensure that your suppliers clearly identify any information they provide with your company and product name and citing the DWI application number.

3.3 Confidentiality

Section 206 (Restriction on disclosure of information) of the Water Industry Act 1991 (WIA)[1] makes it a criminal offence for anyone to disclose information, with respect to any particular business which has been obtained by virtue of any provisions of the WIA and which relates to the affairs of an individual or particular business [2]. In line with the WIA and government policy, the DWI has procedures in place to ensure that information regarding product formulation and ingredients remains confidential.

As the DWI and its expert advisers are already bound, by law, to keep information confidential and cannot contract out of these obligations, the DWI and its expert advisers cannot enter into confidentiality agreements (Non-Disclosure Agreements (NDA)). However, any company confidential information will be treated as covered by the restriction on disclosure under section 206 of the WIA.

DWI may also require your suppliers to provide “confidential” information. If the supplier refuses to provide this information, it may not be possible to progress the application.

For further information see FAQ3.

3.4 Timescale

The time taken to obtain approval is dependent on many factors and delays can be caused by the following:

  1. the completeness of the documentation submitted to DWI
  2. responses from applicants and suppliers
  3. issues with information provided from suppliers
  4. availability of the test laboratory
  5. the results of leaching tests (including BS 6920 testing) and the quality of the leaching test report
  6. the complexity of the application

In view of the various factors, it is not possible to give specific assurance about the time taken to determine an application for approval. DWI cannot assume responsibility for the time taken by the applicant (and any of the applicant’s suppliers) to submit a completed application of sufficient quality.

It is essential that applicants plan ahead and ensure that their applications (including all supporting documentation) are complete and meet all the appropriate requirements. DWI cannot be held responsible for any financial loss arising as a result of the time taken to handle an application, including the potential need for additional information or additional testing work required during the processing of the application.

The progress of submissions from applicants is most often delayed by inadequate or incomplete information. It should be noted that DWI cannot provide consultancy assistance in the completion and submission of an application for approval; however for novel products or complex product applications, a meeting with DWI may be required. Applicants may find it helpful to engage/commission appropriately experienced independent consultants, such as from one of the designated test laboratories, to assist with their application.

3.5 Cost of Application

The cost of applications varies dependant on the complexity of the product. DWI utilises a fixed tier cost system, which is kept under review.

3.6 Formulation requirements

The following requirements should be provided by the applicant, supplier or a combination of both. If, when submitting the application, the applicant does not have full disclosure of the formulation, it should be indicated on the submission that the information will be provided by their supplier(s). The indication will autogenerate a letter to be submitted to their supplier requesting the information.

The product

The following formulation information is required, in English:

  1. details of all constituent components
  2. chemical and trade name of each component
  3. CAS number(s) of each component
  4. Concentration of each component present – the sum of the concentrations should come to 100%
  5. the name of the supplier of each component – where more than one source is used, all alternative suppliers should be named
  6. the Material Safety Data Sheets for each component
  7. Technical datasheet for each component
  8. the method(s) of manufacture and details of the intended use including any components used that do not form part of the final product.

3.7 Alternative Ingredients

For good commercial reasons it is often desirable to have several sources for one or more of the ingredients of materials. However, approval under the requirements of regulation 31 is granted on the basis there will be no changes in the nature or source of the ingredients used in products. If only one source is included in the initial application, any final approval will be based upon the sole use of this source. Adding an additional source will necessitate a request for a change to the approval from DWI.

It is advised to consider any likelihood of wanting to use alternative suppliers for one or more of the ingredients in products and to include these with your initial approval application. In this latter case, we will require full formulation details from each of the proposed suppliers of the ingredient(s). Some (usually minor) additional testing may be required to cover the alternative supplier(s).

3.8 Reworked/Recycled Products/components

DWI accepts that in many cases, good manufacturing practice and economic considerations lead to the practice of using reworked/recycled materials in the manufacture of thermoplastic products ranging from pipes and their fittings and ancillaries, to thermoplastic elastomer (TPE) seals. The reworked/recycled material, including that from other production lines or sources, is not normally acceptable for consideration under regulation 31 (4)(a). Advice should be sought from DWI.

All reworked/recycled material for use in products shall be included in the application, whilst also meeting the following requirements –

  1. Be derived solely from the production line for the final product for which approval is sought, and
  2. Be subject to no change whatsoever (e.g. addition on any ingredients) and only subject to minimal processing, e.g. re-grinding, and
  3. Be under the full control of the manufacturer at all times, i.e. will have been within the specific product manufacturing facilities at all times.

3.9 Substances of concern

The following substances are of concern, but this list is not exhaustive.


The Government policy towards the use of lead as a component in construction products is that it should be avoided whenever alternative safer products are available.

Coal-tar derived bituminous substances

The Government policy towards the use of coal-tar derived bitumen as a component in construction products in contact with drinking water is that it should be avoided whenever alternative safer products are available. See additional information in Advice Sheet 10.


Where a dye is used to colour a treatment chemical, but is not an active ingredient, a food grade dye should be used wherever possible.

4. Leaching Tests

Leachate tests are undertaken as part of the approval process to ascertain compounds of concern either through specific determinand or general screening testing, to ensure the product is suitable for contact with water intended for human consumption and has no adverse effect on water quality that may pose a risk to public health or consumer acceptability.

Advice should always be obtained from DWI before any leachate studies are undertaken.

The following details may be used in order determine suitability:-

  1. Leaching tests and analysis of leachates are required for many applications, e.g. most construction products, membrane filter units etc.
  2. Test Analysis. The specification for leachate analysis is based on the formulation of the product and its method of use. This is provided to the applicant when formulation and IFU have been evaluated.
  3. The analysis, which involves the identification and quantification of specific potentially toxic substances and a general screen by GCMS (identification and semi-quantification) for other substances, provides the basis for the DWI and its expert advisers to evaluate whether use of the product in contact with water might affect drinking water quality, particularly in regard to its aesthetic quality or potential risk to the health of consumers.

4.1 Test Samples

Upon receipt of test requirements issued by DWI, applicants are advised to liaise with their chosen designated test laboratory concerning the choice and/or preparation of test samples taking into account;

  1. For factory made products the elapsed time between test sample manufacture and start of testing – this should be representative of the shortest time likely to be encountered between manufacture and installation and use.
  2. Packaging for sending samples should be suitable by either as supplied from the applicant to the water company, or via liaison with the test laboratory for specially sized pieces.

4.2 Start of Testing

  1. Applicants are normally advised not to commission leaching tests before being notified by DWI about the type of leaching test and the analysis to be performed. Furthermore, applicants must ensure that tests are carried out in accordance with those instructions.
  2. Leachate studies on test samples of site applied and in-situ applied products should start immediately after completion of the minimum cure period specified, at the lowest temperature specified in the Instructions for Use, including any relevant pre-commission treatments.
  3. Leaching tests must be carried out by a designated test laboratory.
  4. Applicants should note that use of a designated test laboratory does not guarantee that a test report will be accepted without question. In certain cases, it may be necessary to ask for additional tests to be carried out, particularly where the test report indicates significant concentrations of unidentified substances or substances of concern.

4.3 Test Reports and Evaluation

These must be clear, unambiguous and supported by appropriate quality assurance data. Failure to satisfy these requirements will delay processing of an application and may lead to refusal of approval by DWI.

All test reports are submitted for evaluation to the analytical expert for confirmation that all the procedures have been correctly carried out. If the report is deemed unsatisfactory, the test laboratory will be asked for comment and/or correction, or, in the worst case, re-analysis. In some cases, the test results may lead to the requirement to carry out additional testing before the outcome of the application can be determined. If either of these are needed, there will inevitably be a delay in the approval process.

Once the test report has been deemed satisfactory by the analytical expert, a toxicological evaluation is undertaken to determine any potential health risks. During this process further information may be required from either the applicant, test laboratory or suppliers.

Once the toxicological assessment has been received, the final assessment of the product application will be undertaken by DWI.

5. Requirements for Toxicity Data

The DWI may ask for toxicity data to help assess the significance on consumers’ health of substances present in the product or identified in leachates. These substances may be components of the product, impurities or by-products of the manufacturing process or substances formed by the reaction of the product or its ingredients with substances present in water. Such data may be available in published literature but is more frequently held by manufacturers in the form of unpublished studies. It is the applicant’s responsibility to approach manufacturers for this data; DWI can act as an intermediary if the manufacturer/supplier is unwilling to disclose the data to the applicant.

In cases where analysis for a specific substance is not technically feasible, the DWI may be prepared to consider a worst-case assessment of the likely concentration of the substance in the leachate. If such calculations become necessary, DWI will advise on the methodology to be followed by the applicant.

6. Approval

Before a product can be approved by the Authorities, DWI and its expert advisers must be satisfied that use of the substance or product will not cause any adverse effect on drinking water quality or present a risk to consumers’ health. DWI does not consider whether a product is fit for its intended purpose and approval by the Authorities must not be misconstrued as a favourable assessment of the performance or merits of any product.

Approval letters, which contain conditions of approval, make it clear that approval only relates to methods of application or use, set out in the Instructions for Use (IFU) documentation submitted to DWI. A condition of approval requires that the product is installed and used solely in accordance with the IFU document, which must be made available to water suppliers or combined licensees by the approval holder.

Instructions for Use must be contained in a uniquely identified controlled document and any revisions must be notified to the DWI (see Advice Sheet 2 for further information and help) before being made.

Product approvals issued by the authorities of Northern Ireland and Scotland are done so based on the approvals granted in England and Wales. It is customary for applicants to receive approval letters from Northern Ireland and Scotland after signed acknowledgement agreeing to the conditions of approval for the approval granted for England and Wales has been returned to DWI.

Approvals will have a 5-year lifespan. Six months prior to this, the approval holder will be sent a courtesy reminder to provide details required to have the product re-approved. It is important that the approval holder ensures that the contact details remain correct so that the request for re-approval can be sent. However, it is the responsibility of the approval holder to ensure a product maintains approval for the water industry to utilise it. The approval holder should ensure that they provide sufficient time for the assessment of the application for re-approval to be assessed when submitting.

All approved products are listed in the List of Approved Products. Listing includes any conditions of approval, details of the IFU and expiry date.

6.1 Approval Claims

Products listed in the “List” are granted approval by the Authorities. DWI operates the approval system on behalf of the Authorities. Information about acceptable claims for approved products in England and Wales is given on the FAQ2

6.2 Refusal, Modification, Revocation or Review of Approval

It may be necessary for DWI to advise the Authorities on approvals that may need to be refused, revoked or modified. Should the approval of a substance or product be refused, or a proposed change to an approved product not granted, a refusal letter is issued. All refusals are published on the DWI website in the “List”. Similar arrangements exist for the notification of revocation or modification of approvals, this may also include the notification to the water industry.

The DWI carries out a systematic review of all approvals. Each product or substance specific review may be undertaken considering information that is pertinent to the approval. Normally, six months’ notice of any subsequent modification to, or revocation of approval is given. However, approval may be revoked without notice in the interests of public health, and water suppliers notified of the revocation with immediate effect.

7. Changes to Approved Products

Any change undertaken on an approved product must be notified to DWI in advance of the change being made. The conditions of approval signed and agreed upon by the approval holder make this condition clear and failure to notify a change in advance may result in product revocation.

For further information on changes and the appropriate charges see Advice Sheet 4.

8. Application Procedure

Applications to the DWI should be made using the appropriate product specific application form. A series of forms are available from the DWI. There are specific instructions and guidance given on the application forms and associated advice sheets to help to ensure that applicants provide the DWI with all the information required about the particular product type. Failure to provide all required information will cause delays to the application or may lead to the receipt of the application being refused until the relevant data is provided.

This process uses an online portal with Government Gateway access as outlined in Advice Sheet 12


  1. A non-consolidated version of the WIA is available to view
  2. Exceptions include: consent of the individual or business concerned and disclosure which is for the purpose of facilitating the performance of certain statutory functions of various bodies (including the Secretary of State, Ofwat and local authorities) – section 206(1) and section 206(3)(a) of the WIA respectively.
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