Water safety certifications for rubber products and ISMAT's Approved Sealing Materials

Every pump, valve and pipe joint in a water system relies on a seal to keep water in and contaminants out. In drinking water applications, that seal has a second job: it must not add anything harmful to the water it touches.

A rubber compound can meet every dimensional and mechanical spec on a drawing and still fail a water safety test. Compounds are formulated with a mix of polymers, curing agents, plasticizers and fillers, and unless that specific formulation has been tested and certified for potable water contact, there’s no way to know whether it’s safe to use. This is why drinking water systems require seals backed by recognized third-party certification.

This blog walks through the major global water safety standards and looks in detail at Cerulean EP 14, ISMAT’s WRAS-approved EPDM compound.

1. How Water Safety Certifications Differ Around the World

Water safety rules vary by region. Each one runs its own testing regime, with its own thresholds and its own list of approved materials. For an OEM selling into multiple countries, this means the seal must carry the specific certification each target market recognizes.

WRAS (Water Regulations Advisory Scheme) — United Kingdom

In the UK, compliance with the Water Supply (Water Fittings) Regulations 1999 is shown through WRAS approval. For elastomers, testing follows BS 6920, “Suitability of non-metallic products for use in contact with water intended for human consumption.”

BS 6920 covers five checks:

1. Oduor and flavor — does the material give the water any detectable taste or smell?
2. Appearance — does it cause discoloration or turbidity?
3. Growth of microorganisms — does it encourage microbial growth in the water, tested in line with EN 16421?
4. Extraction of substances (cytotoxicity) — cell culture testing to rule out cytotoxic or mutagenic leachates.
5. Extraction of metals — checks for leached lead, cadmium, arsenic and other harmful trace metals.

WRAS approvals are tied to a temperature band — typically cold water up to 23°C or hot water up to 85°C — and need to be renewed every five years.

NSF/ANSI/CAN 61 — North America

In the US and Canada, the standard that matters are NSF/ANSI/CAN 61. It sets health-based limits on what a component is allowed to leach into drinking water.

Getting certified involves:

• Extraction testing under simulated conditions across different water chemistries, including commercial hot water up to 82°C (180°F).
• Toxicological review of the leachates against established drinking water health limits, including PFAS.
• Unannounced plant audits, both at initial certification and on an ongoing basis, to confirm the formulation stay consistent over time.

KTW-BWGL and DVGW W270 — Germany

Germany’s requirements, set by the Federal Environmental Agency (UBA) under the German Drinking Water Ordinance, are among the strictest in Europe.

• KTW-BWGL works on a positive-list basis — every monomer and additive in the compound must already be on the approved KTW list, on top of migration and taste/odour testing.
• DVGW W270 looks specifically at microbiology: whether the rubber surface promotes biofilm formation or microbial growth under standard flow conditions.

KIWA (BRL-K17504) — Netherlands

The Dutch Kiwa Watermark, governed by BRL-K17504, is required for vulcanized rubber seals used in Dutch cold and hot water systems. It combines two things a lot of certifications keep separate:

• Hygiene — migration limits and organoleptic testing, similar to WRAS and NSF.
• Mechanical performance — Kiwa also checks the seal against EN 681-1, the European standard for the physical properties of elastomeric pipe seals, covering whether the seal holds up in service over the long term.

2. ISMAT’s WRAS-Approved Material: Cerulean EP 14

1. For drinking water applications, ISMAT’s approved material is an EPDM compound: Cerulean EP 14, listed in the WRAS Materials Directory under the formulation reference ISM70EPW, Approval Number 240755071.
2. EPDM is the usual choice for water contact seals because of how its polymer backbone behaves. Certification status varies from compound to compound, though, which is why Cerulean EP 14 is made with high-purity raw polymer and processed under audited, controlled conditions specifically to hold WRAS approval while keeping its mechanical performance.

Mechanical and thermal properties (70 Shore A)

What it resists

• Hot water and steam — EPDM’s saturated backbone gives it good hydrolytic stability, so it doesn’t swell or degrade under repeated hot water exposure or steam sterilization.
• Ozone, UV and weathering — the same saturated structure resists cracking from ozone and sunlight, which matters for outdoor pipework as much as indoor plants.
• Low-temperature service — it stays flexible down to -55°C without going brittle, which is relevant for installations that see freezing conditions.
• Chlorine and chloramines — it holds up well against the disinfectants used in treated drinking water and against moderate CIP chemicals.

One limit worth flagging: Cerulean EP 14, like other EPDM compounds, is not compatible with mineral oils, fuels or heavy hydrocarbons. If a system has any exposure to these, EPDM is the wrong material regardless of its water certification.

3. Where This Material Gets Used: Seal Configurations

WRAS approval covers the compound, but the compound gets converted into different seal geometries depending on where it sits in the system. ISMAT manufactures Cerulean EP 14 across the following configurations:

• O-rings — the most common static and dynamic seal, used in pump housings, valve stems, filters and quick-connect couplings.
• Backup rings — fitted alongside a primary seal in high-pressure applications to stop the elastomer from extruding into clearance gaps.
• U-cup and lip seals — built for dynamic linear and rotary sealing in pumps and hydraulic cylinders, where low friction and steady lip contact matter.
• X-rings (quad-rings) — a four-lobed profile that gives multiple sealing contact points and resists rolling or twisting in the groove better than a standard O-ring.
• Wiper seals — scrape mud, dust and particulates reciprocating shafts before they can reach the primary seal.

These parts show up at every stage of a water system — intake, filtration, chemical dosing, storage and distribution.

4. Choosing a Seal for Potable Water: What Actually Matters

A few things that engineering and procurement teams tend to overlook when specifying water-contact seals:

Specify the exact compound. A standard commercial EPDM may use plasticizers or sulfur curatives that would fail a taste or toxicology test. Specify the certified reference directly (Cerulean EP 14 / ISM70EPW) and get the current certificate from the manufacturer.

Check the certified operating window. WRAS approval for ISM70EPW applies up to 85°C for domestic hot water, tested at a specific section radius. Running the seal outside those conditions takes it outside the certification too, even though the part number stays the same.

Weigh hygiene and mechanics together. A hygiene-certified compound still has to survive the system it’s installed in. Check compression set and tensile strength against the actual pressure and groove geometry. If the water line involves aggressive chemical dosing — high-concentration hypochlorite, acids, alkalis — cross-check that against the material’s chemical resistance chart before finalizing the spec.

A certification like WRAS is a reasonable proxy for a compound that was actually tested against the conditions it will see in service, which is why it’s worth specifying by name.

ISMAT has been manufacturing high-performance sealing solutions from Chennai since 1981, supplying oil and gas, water treatment and chemical processing industries worldwide. Cerulean EP 14 (ISM70EPW) is one part of a wider Cerulean range built to the certifications each market actually requires, not just to a generic material spec. If you are specifying seals for a drinking water or water treatment application, reach out to our engineering team with your operating conditions and we’ll help you get to the right compound and certification.