Water-treatment chemicals include flocculants, coagulants and disinfectants used by water companies and industrial users to treat water from source to the point of delivery. Products that come into contact with drinking water in England and Wales generally require approval from the Drinking Water Inspectorate (DWI), which is a key consideration when sourcing this type of product.
Key points
- Regulation 31 of the Water Supply (Water Quality) Regulations 2016 governs approval of chemicals and materials in contact with drinking water in England and Wales.
- Treatment chemicals not covered by a relevant BS EN standard - including many flocculants, coagulants and disinfectants - generally need DWI approval before use by a water undertaker.
- Products fully conforming to an appropriate BS EN standard do not need separate Regulation 31 approval.
- DWI approval is typically held by the manufacturer or formulator, so confirm approval status before committing to a supplier for regulated water-treatment products.
Products Typically Manufactured
Contract manufacturers in this sector produce flocculants and coagulants for water clarification, disinfection chemicals, pH adjusters, and specialist treatment chemicals for both potable water and industrial water treatment applications.
Common Manufacturing Processes
Water-treatment chemicals are typically produced through liquid chemical blending or aqueous blending, with some products requiring reaction chemistry. Finished product is filled and packed into IBCs, drums or smaller containers depending on the customer's scale of use.
Regulatory Considerations
The Drinking Water Inspectorate operates the Regulation 31 approval system for products and materials in contact with water intended for human consumption, from abstraction through to delivery at the customer's premises. Treatment chemicals not covered by an appropriate BS EN standard generally require this approval before a water undertaker can use them. If your product is intended for use by a UK water company, confirm the manufacturer's approach to DWI approval directly, as approval is specific to the formulation and manufacturer.
Why Businesses Use Contract Manufacturing Here
Water-treatment chemical manufacture combines specialist blending capability with regulatory approval processes that take time and expertise to navigate, making an established manufacturer with existing DWI-approved products a practical route for new entrants - see contract chemical manufacturing in the UK.
Approval Requirements
Products intended for use in drinking water supply face approval requirements in addition to general chemical regulation, and using an unapproved product in that application is not permitted regardless of how well it performs. Approval covers the product as formulated, so changes to a formulation can require reapproval - which makes change control unusually consequential here.
Where a product has a biocidal function, the biocidal products regime may apply as well, covering both active substance and product. Establishing which requirements apply before development rather than after is important, because approval timelines routinely exceed manufacturing lead times by a wide margin.
Manufacturing Considerations
The sector uses a wide chemistry range, from simple inorganic salts to speciality polymers and biocides, so manufacturing requirements vary considerably by product. Many are corrosive or oxidising, requiring compatible materials of construction - see corrosive chemical processing.
Bulk supply in IBCs and tankers is common, and dosing accuracy in use means product concentration consistency matters more than in sectors where the user adjusts by eye. Purity requirements can also be tight, since trace contaminants entering a water supply are a different matter from trace contaminants in an industrial product.
Questions to Ask a Manufacturer
- Does your product, or can our formulation, hold Regulation 31 (DWI) approval?
- What quality testing do you carry out on each batch of treatment chemical?
- What container sizes and delivery formats do you offer for water company customers?
- What is your experience supplying UK water utilities directly or through distributors?
Related Pages
Frequently Asked Questions
Do all water-treatment chemicals need DWI approval?
No - products fully conforming to an appropriate BS EN standard don't need separate Regulation 31 approval, but many flocculants, coagulants and disinfectants without such a standard do.
Can I get DWI approval myself if my contract manufacturer doesn't have it?
Approval is generally sought for a specific product and formulation, so this depends on your arrangement with the manufacturer - discuss who holds or will hold the approval before committing to a supplier.
Find a Manufacturer
Find a UK Contract Chemical Manufacturer
Search the directory of UK contract and toll manufacturers by process, industry and capability.
Search the DirectoryLast reviewed: August 2026. Regulation and guidance change — verify anything you rely on against the primary source. Tell us if something here is out of date.