Ensuring the Safety and Compliance of Materials for Potable Water

Ensuring the safety and compliance of materials in contact with drinking (potable) water is a critical responsibility for engineers, manufacturers, and contractors in the UK. The Water Regulations Advisory Scheme (WRAS) provides a robust framework to certify materials for potable water use, verifying that products will not compromise water quality, public health, or system performance.

Is WRAS Approval a Legal Requirement?

While WRAS approval itself is a voluntary certification and not a legal requirement, compliance with the Water Supply (Water Fittings) Regulations (or Scottish Byelaws) is mandatory by law.

In the context of O-rings, this means:

• The Legal Risk: Installing a non-compliant O-ring, such as a generic automotive seal, that leaches chemicals or promotes bacterial growth is a criminal offense.
• The Performance Gap: In the UK, compliance is viewed through two lenses: Safety (BS 6920/WRAS) and Reliability (EN 681-1). While WRAS ensures the water stays pure, EN 681-1 (the standard for elastomeric seals) ensures the O-ring is physically strong enough to prevent leaks and structural failure.
• The Practical Solution: Because individual homeowners and plumbers cannot easily perform laboratory tests on a single rubber seal, using WRAS-approved O-rings is the only practical way to guarantee that a component meets the required legal standards for both safety and mechanical integrity.

The regulations state that every water fitting must be of "an appropriate quality and standard." While other certifications (like KIWA or NSF) are also legally valid, WRAS remains the most recognised "stamp of approval" in the UK to ensure your plumbing stays on the right side of the law.

What WRAS Approval Ensures

WRAS certification confirms that materials and components in contact with potable water:

• Do not leach harmful substances into water.
• Maintain taste, odour, and clarity.
• Prevent microbial growth (Standardised via EN 16421).
• Retain structural integrity under normal service conditions (Standardised via EN 681).

Materials undergo rigorous testing, including:

• Chemical extraction testing: Ensures no harmful compounds migrate into water.
• Organoleptic assessment: Evaluates taste and odour impacts.
• Microbial growth testing (EN 16421 / BS 6920-2.6): Ensures the material does not provide a "food source" for bacteria. EN 16421 tests the Enhancement of Microbial Growth (EMG), preventing biofilms that could harbor pathogens like Legionella.
• Mechanical performance (EN 681-1): Verifies hardness, tensile strength, and "compression set" to ensure the seal doesn't degrade over time.

Only materials that meet all criteria are approved, providing confidence in long-term water safety for engineers, contractors, and water authorities.

Scope of WRAS-Certified Products

WRAS certification is relevant to non-metallic components in contact with potable water, including:

• Seals and gaskets
• O-rings
• Cords
• Tubing and hoses
• Sheets and linings
• Rubber mouldings

Checking WRAS Approval

• Verify that a product has a current WRAS approval mark.
• Approvals are valid for 5 years and must be re-evaluated after expiration.
• Formulations can change over time; only verified approvals ensure regulatory compliance.
• Manufacturers display the WRAS Certification Mark on packaging or websites.
• Check out the official Polymax WRAS listings on the WRAS website.

Key point: WRAS approval covers individual products or materials, not an entire manufacturer’s product range.

WRAS vs Global Potable Water Standards

Elastomer and Non-Elastomer Material Comparison

Selecting the correct elastomer or material is critical for WRAS compliance. Only chemically inert, water-stable, and microbiologically safe materials should be used in drinking water systems.

WRAS at a Glance

• Chemical safety (via BS 6920)
• Microbiological safety (via EN 16421)
• Mechanical reliability (via EN 681)
• Regulatory compliance (Water Supply Regulations 1999)

For UK potable water applications, engineers and specifiers should prioritise WRAS-approved Silicone (VMQ) and EPDM, as these consistently meet stringent testing requirements.

Tip: Always verify material WRAS status and consult technical datasheets to ensure safe, compliant, and long-lasting potable water systems.

Get Expert Advice

Our team of experts can help you choose the right materials for drinking water applications, ensuring WRAS compliance and UK regulatory adherence.

Contact us: +44 (0) 1420 474 123 | Email: sales@polymax.co.uk

When it comes to passenger safety in public transport, material choice is critical. Around half of all fire-related casualties are not linked to flames, but to the inhalation of smoke and toxic gases. For manufacturers and operators in the rail sector, the challenge is clear: select materials that limit ignition, reduce flame spread, and minimise smoke and toxicity.

Polymax is bringing the latest in material innovation with the introduction of Polymax TRail® EN45545-certified rubber compounds. These compounds have been developed by Polymax’s in-house chemists and independently certified by a COFRAC accredited laboratory, ensuring compliance with the highest international safety standards.

Why EN45545 Matters

The EN45545-2:2013+A1:2016 standard governs the fire behaviour of materials used in rail and transport applications, classifying them by hazard level depending on their use inside or outside carriages. The goal is simple but vital: to restrict fire development and provide passengers and staff valuable time to reach safety.

The approved compounds meet the most demanding of these classifications:

• Polymax TRail® R10 HL3 – SE 75
• Polymax TRail® R22/23 HL2 – RE 75

Tested for Safety, Proven in Performance

The compounds have undergone rigorous testing across key fire performance measures:

• ISO 9239-1 Critical Flux Test – Demonstrates resistance to flame spread; Polymax compounds showed excellent performance in limiting flame propagation.
• ISO 5660-1 Rate of Heat Release – Using a cone calorimeter, the compounds achieved a low Maximum Average Rate of Heat Emission (MARHE), indicating slower heat release and reduced fire intensity.
• ISO 5659-2 Smoke Density and Toxicity – Tests confirmed low smoke generation with significantly reduced emission of toxic gases, a major factor in improving survivability during a fire.
• ISO 4589-2 Oxygen Index – Both compounds required a high minimum oxygen concentration to sustain combustion, showing strong resistance to ignition in real-world scenarios.

These results place Polymax EN45545 compounds firmly among the most reliable solutions for safety-critical rail applications, e.g. in the form of extrusions, mouldings and hoses.

To find out more contact us 

We are often asked questions like: “What’s the difference between a gasket, a seal, and an O-ring?” It’s a great question, and understanding these distinctions will ensure you choose the right sealing solution for your application.

At first glance they may appear to be the same, but when it comes to keeping fluids, gases, or contaminants where they belong, gaskets, seals, and O-rings., each has a unique role in maintaining the integrity of the systems they protect. Choosing the right one is critical for performance, safety, and efficiency.

In this article, we will break down the differences between gaskets, seals, and O-rings, and explain when to use each.

Regardless of the type of seal,  material selection for gaskets, seals, and O-rings is always based on operating criteria such as temperature range, pressure, chemical compatibility, regulatory approval, and mechanical performance.  A common approach that ensures whether your application requires a gasket, seal or O-ring it will deliver reliable sealing in its intended environment.

What is a Gasket?

A gasket is a flat or shaped component that sits between two mating surfaces to primarily prevent leaks, the ingress of any foreign body, and in certain applications reducing noise transfer. Typically compressed between flanges, housings, or covers, gaskets create a tight seal under pressure.

• Materials: Can be manufactured in a wide range of materials including, Rubber (EPDM, Viton®, Nitrile), compressed fibre, graphite, PTFE, metal, or composite laminates.
• Common Uses: Flanged pipe joints, pumps, heat exchangers, automotive applications, HVAC systems, electrical enclosures etc.
• Key Benefits:
  • Excellent for irregular or uneven surfaces
  • Wide choice of materials for chemical, temperature, or fire resistance
  • Can be cut or moulded to suit complex shapes

Short description: Gaskets seal static joints between rigid surfaces.

What is a Seal?

A seal can be used as a generic term to include any component designed to prevent leakage or ingress of fluids, dust, or gases.

However, unlike gaskets, seals are often employed to deal with dynamic applications where there is relative motion at the intersection between moving components, such as rotating shafts or piston rings.

• Types of Seals: Oil seals, mechanical seals, rotary shaft seals, lip seals.
• Materials: Elastomers, PTFE, polyurethane, sometimes bonded to metal for rigidity.
• Common Uses: Pumps, gearboxes, bearings, engines, and hydraulic systems.
• Key Benefits:
  • Withstands movement and pressure
  • Protects against contamination (dust, dirt, water)
  • Extends equipment life

Short description: Seals can cover static applications, but primarily cover dynamic applications, providing a seal between moving parts.

What is an O-Ring?

An O-ring is one of the simplest and most commonly used sealing components. It is a doughnut-shaped ring of elastomer that sits in a groove and compresses between two surfaces.

• Materials: Nitrile (NBR), EPDM, FKM/Viton®, Silicone, PTFE.
• Common Uses: Hydraulic fittings, pneumatic systems, plumbing, automotive, aerospace, food and pharma.
• Key Benefits:
  • Simple, low-cost design
  • Works in static and dynamic environments
  • Standard sizes readily available (BS, AS, ISO ranges)

Short description: O-rings are compact, versatile, and ideal for both static and moving applications.

Gasket vs Seal vs O-Ring — Key Differences

A quick guide to choosing the right option.

• Use a gasket if you are sealing two static, flat surfaces such as flanges.
• Choose a seal if your application involves movement (shafts, rotating parts).
• Select an O-ring when you need a simple, versatile, and low-cost solution for either static or dynamic sealing.

To make sure you make the right choice contact our team