Specifying rubber for water infrastructure is not the same as specifying rubber for any other industrial application. The moment a rubber component comes into contact with drinking water at a treatment works, distribution main or a service reservoir, an entirely different set of requirements applies. Getting it wrong is not an option – it is a public health and regulatory necessity all organisations in the sector must meet.
This guide is written for procurement managers, engineers and technicians working in and around UK water infrastructure: at water companies, at civil and mechanical contractors, and at the specialist suppliers that service them.
It walks you through what WRAS approval actually means, which rubber compounds carry approved grades, where rubber is commonly used across water infrastructure and what Walker Rubber needs from you to confirm compliance for your application.
You can also view our full rubber for the water industry product range here.
What is WRAS Approval in Rubber Manufacturing?
WRAS stands for the Water Regulations Advisory Scheme. The WRAS approval process tests products and materials that come into contact with drinking water to verify that they do not contaminate it. A WRAS-approved rubber product has been independently tested and confirmed to meet the requirements of Regulation 4 of the Water Supply (Water Fittings) Regulations 1999: the legal framework governing anything installed in or connected to the UK public water supply.
The best methodology follows BS 6920, which assesses whether material causes taste, odour, turbidity, or growth of microorganisms in water at the concentrations encountered in service. WRAS approval is not a quality mark but a specific, evidence-based regulatory compliance status.
Who Needs to Get WRAS Approval?
Water companies including Thames Water, Severn Trent, Yorkshire Water and all other regulated UK utilities companies require WRAS-approved materials for all components in direct contact with potable water. This requirement flows down to the civil and mechanical engineering contractors working on their networks too, and to the component suppliers who serve those contractors.
Any rubber product specified for a drinking water application in the UK should carry WRAS approval, or be accompanied by alternative evidence of compliance with BS 6920.
What Happens if You Don’t Use WRAS-Approved Rubber?
A non-approved compound in a drinking water application may leach plasticisers, accelerators, or other chemical constituents into the water. Even at trace concentrations, this can cause taste and odour complaints, trigger regulatory non-compliance notices, and in the most serious cases affect drinking water safety.
Commercially, specifying non-approved materials on a water company framework project is a significant liability. If non-compliance is discovered during inspection or installation audit, it can require removal and replacement, delay handover, and damage supplier standing. The requirement to use WRAS-approved materials is a contractual and regulatory obligation on any project throughout the public water supply system – not merely a best practice.
Which Rubber Compounds Have WRS-Approved Grades?
Not all rubber compounds are available with WRAS approval, and within those that are, not all grades or formulations will have been tested and listed. Approval is compound-specific and formulation-specific: a WRAS-approved EPDM formulation does not automatically extend to all EPDM compounds. The compounds most commonly specified with WRAS-approved grades in water infrastructure are:
EPDM
The most widely used compound in water industry application. Available in WRAS-approved formulations across a broad hardness range. Its resistance to weathering, ozone, and wide temperature variation makes it suitable for both underground and above-ground operations, and its low extractable content (the property that makes it chemically stable in contact with water) is well established. WRAS-approved grades are available in solid, sponge and co-extruded forms. For most gate seals, pipe gaskets, expansion seals and access cover seals, WRAS EPDM extrusions are common throughout the industry.
Nitrile (NBR)
WRAS-approved grades are used where the application involves both water contact and exposure to petroleum-based products, e.g. at treatment works where machinery lubricants may be present, or in combined services applications. Nitrile’s oil and fuel resistance is essential in these environments; standard EPDM would swell and degrade. WRAS Nitrile extrusions often represent a more specialist specification than EPDM.
Natural Rubber (NR)
It retains a place in the water industry, particularly for large gate seals and sluice gate face seals where its high tensile strength and resilience under heavy compressive loads are valuable. WRAS-approved natural rubber grades are available and continue to be specified by some water authorities, though EPDM has displaced natural rubber in many newer installations due to its superior weathering resistance, durability and longevity.
Silicone
In WRAS-approved grades, silicone is used where high-temperature water applications are involved, such as in treatment processes with elevated temperatures, or in hot water service components. Silicone extrusions offer stable performance across a very wide temperature range, but this material can be an unnecessarily expensive choice for ambient-temperature water infrastructure applications.
In all cases, the starting point for specification is to confirm that the compound formulation being proposed carries a current, valid WRAS listing. WRAS approval is time-limited and must be maintained through periodic re-testing; an approved formulation from a supplier who has not maintained their listing is no longer compliant.
Where is Rubber Used in Water Infrastructure?
Rubber components appear throughout the water supply and wastewater chain, often in applications where failure is difficult and costly to remediate.
Gate Seals and Sluice Gate Seals
Among the most demanding rubber applications in water infrastructure. A gate seal provides the watertight contact face between a sluice gate and its frame; the rubber compresses under the gate’s seating load and must maintain an effective seal against full operating head. These seals are typically larger, produced from solid EDM or natural rubber in WRAS-approved grades, and must perform reliably through repeated open-and-close cycles over decades of service. Profile geometry is application-specific; most gate seals are customer-extruded to the gate manufacturer’s or contractor’s drawing.
Expansion Joints and Flexible Connectors
These components accommodate movement between pipework sections caused by thermal expansion, ground settlement, and dynamic loads. The rubber elements must seal reliably under pressure while tolerating repeated deformation. WRAS-approved expansion seals in EPDM are standard for drinking water applications; profile and dimensional specification is typically defined by the pipeline engineer.
Pipe Gaskets and Flange Seals
Used throughout the distribution network at every bolted joint, valve connection and meter installation. These are often cut from WRAS-approved rubber sheet or produced to standard BS EN dimensions. Walker Rubber’s gasket range includes CNC machine cut and water jet-cut options suited to water industry applications. The gasket must compress evenly around the flange face and maintain a long-term seal under bolt load and operating pressure.
Valve Seals
Gate valve face seals, ball valve seals, and butterfly valve liners use moulded WRAS-approved rubber to create the sealing surface that closes off flow. Butterfly valve liners in particular are a significant application in water distribution, where the rubber liner provides both the seating face and a degree of corrosion protection to the valve body.
Access Cover Seals and Manhole Frame Gaskets
Provide weatherproofing and water exclusion for below-ground chambers. Here these are within the water supply boundary, WRAS-approved materials may be specified. Extruded EPDM profiles are common in this application.
Extrusions, Moulding & Gasket Cutting: Which Process for Which Application?
Water industry rubber applications span all three primary rubber manufacturing processes. Our Knowledge Hub covers each one in detail:
→ Read about: Extruding rubber parts
→ Read about: Moulding rubber parts
→ Read about: Cutting rubber parts
Extrusion
Rubber extrusion is the process of choice for continuous-length profiles: gate seal sections, expansion seal strips, pipe wrapping profiles, and any application where a constant cross-section runs along a length. Custom extrusion allows the profile geometry to be optimised for the seating load and compression distance of a specific gate or joint design. Walker Rubber’s in-house tooling means customer profiles for water applications can be produced quickly, with samples available within 72 hours of tooling completion.
Rubber Moulding
Compression, transfer or injection moulding are appropriate for discrete components with three-dimension geometry: valve seats, butterfly valve liners, moulded corner pieces for gate seal sets, and specialist pipe couplings. Walker Rubber’s moulding capability, strengthened through our Clingbrook acquisition, cover the range of component sizes found in water infrastructure.
Gasket Cutting
Cutting gaskets from WRAS-approved rubber sheet covers standard and non-standard flange gaskets, joint rings and sealing washers. CNC cutting from sheet allows bespoke profiles to be produced quickly without tooling investment – useful for non-standard flange dimensions or legacy pipework where standard gaskets do not fit.
How to Enquire: What Walker Rubber Needs to Confirm WRAS Compliance
Making a WRAS-compliant rubber enquiry is straightforward with the right information. Contact the Walker Rubber team with the following:
The application
Specifically, will the rubber be in direct contact with potable drinking water? The WRAS requirement applies to drinking water contact; applications in wastewater infrastructure have different regulatory requirements.
The component type
Gate seal, pipe gasket, expansion seal, valve seat, or other. This determines whether the requirement is for an extruded profile, a moulded component, or a cut gasket.
The drawing or sample
A profile cross-section drawing, dimensional diagram, or physical sample of the existing component. Relevant standards (BS EN 1514 for pipe flanges, for example) should be included where available. Our Knowledge Hub article on rubber engineering tolerances is a useful reference if you are uncertain what tolerances to specify.
The compound requirement if known
WRAS EPDM covers most applications, but if a specific hardness, food-grade certification, or specialist compound (Nitrile, Silicone) is required, that should be stated.
Quantity and delivery requirement
Make-to-order from 48 hours for standard profiles; longer for complex moulded components or large gate seal sets. Walker Rubber will confirm the WRAS status of the proposed compound formulation as part of the quotation.
Walker Rubber manufactures WRAS-approved rubber extrusions, gaskets, and moulded components from Norwich, UK. Custom profiles with no minimum order quantity and lead times from 48 hours.
Contact the team for a same-day quotation and confirmation of WRAS compliance status for your application.