Sealing materials for contact with drinking water

Seals in contact with drinking water perform a central safety function within drinking water installations. They prevent leaks, safeguard the hygienic quality of the water and often remain in permanent contact with a particularly sensitive medium over many years. Even minor material changes, migration or unsuitable formulations can have a direct effect on drinking water quality. Accordingly, the technical, hygienic and legal requirements for sealing materials for this field of application are high.

In contrast to classic industrial applications, the mechanical function is not the sole priority for drinking water seals. What is decisive is rather material purity, long-term stability, sensory neutrality and a clearly proven suitability in accordance with the applicable regulations.

Why special sealing materials are necessary in the drinking water sector

In Europe, drinking water is among the most strictly monitored foods. All materials that come into contact with drinking water must neither release substances relevant to health nor alter the odour, taste or appearance of the water. Even the smallest quantities of plasticisers, residual monomers or degradation products can be critical.

Conventional seals from general mechanical engineering or plant construction generally do not meet these requirements. They are often optimised for oil resistance, chemical resistance or mechanical load capacity, but not for hygienic long-term applications involving water. The use of unsuitable materials can lead to contamination, material degradation or loss of function in the long term.

Legal requirements and relevant standards

Binding regulations apply to sealing materials in contact with drinking water in Germany and Europe, ensuring hygienic suitability:

• KTW-BWGL regulates the hygienic assessment of organic materials in contact with drinking water. It defines test methods, limit values and migration requirements for elastomers and plastics.
• DVGW approvals confirm the suitability of products and materials for use within drinking water installations and are particularly relevant in the sanitary and supply sector.
• Recommendations of the German Environment Agency (UBA) form the basis for assessing hygienic risks and feed directly into national regulations.
• The EU Drinking Water Directive ensures Europe-wide harmonisation of the requirements for materials in contact with drinking water.

Only seals whose material composition has been tested and documented may be used permanently in drinking water systems. A mere material designation without a specific approval is not sufficient for this.

Suitable sealing materials for contact with drinking water

EPDM

EPDM is one of the most important and most frequently used elastomers in the drinking water sector. The material offers very good resistance to water, steam and hot water and is characterised by high ageing and ozone resistance. Due to its stable polymer structure, EPDM shows only a low tendency to migration.

EPDM grades with KTW-BWGL and DVGW approval are preferably used in hot and cold water pipes, pipe connections, fittings, valves and in sanitary engineering. The tested formulation is always decisive here, as not every EPDM compound is automatically suitable for drinking water.

Silicone

Silicone seals are used above all where high temperature ranges, high elasticity or special requirements for flexibility exist. Silicones suitable for drinking water are physiologically harmless, odourless and tasteless and show very good recovery behaviour.

Typical areas of application are household appliances with a drinking water connection, filter systems, dosing systems and sensitive applications with changing temperatures. However, silicone has a lower mechanical load capacity than EPDM and is therefore used in a targeted manner and depending on the application.

NBR (suitable to a limited extent)

NBR is used in the drinking water sector only under certain conditions. Specially formulated and tested NBR grades can obtain a drinking water approval, in particular for applications with higher mechanical stress or certain sealing geometries.

Suitability depends strongly on the specific formulation. Without corresponding approval, NBR is not suitable for permanent contact with drinking water.

Sealing materials with restrictions or exclusion

FKM (Viton)

FKM offers excellent chemical and thermal resistance and is frequently used in demanding industrial applications. However, for contact with drinking water the material is suitable only in exceptional cases. Without special tests and approvals there is an increased risk of substance migration.

For this reason, FKM is predominantly used for technical media, process fluids or industrial applications outside drinking water installations.

Natural rubber and untested elastomers

Natural rubber as well as untested elastomer compounds are unsuitable for direct contact with drinking water. They can release organic constituents, odorous substances or undesirable by-products and often undergo rapid ageing in contact with water.

The use of such materials represents a hygienic risk and is not permitted in drinking water systems.

Typical areas of application for drinking water seals

Sealing materials with drinking water approval are used in numerous areas:

• Drinking water pipes and pipe connections
• Fittings, valves and shut-off devices
• Water meters, backflow preventers and filter systems
• Sanitary engineering in residential and commercial buildings
• Industrial drinking water systems and supply installations

In all these applications, permanent material stability is just as relevant as proven hygienic harmlessness.

Selection criteria for practice

When selecting suitable sealing materials for contact with drinking water, several factors should be systematically taken into account:

• Existing drinking water approval and documented test marks
• Temperature range of the medium as well as possible temperature fluctuations
• Pressure load and mechanical stress
• Contact time and expected service life of the seal
• Sealing geometry and installation situation

A material-appropriate selection considerably reduces failure risks, maintenance effort and hygienic uncertainties.

Common mistakes in material selection

In practice, typical mistakes occur time and again:

• Use of untested standard seals without drinking water approval
• Equating food approval with drinking water approval
• Neglecting temperature and pressure requirements
• Missing or incomplete documentation of the material approval

These mistakes can lead to functional faults or hygienic problems in the long term.

In conclusion

Sealing materials for contact with drinking water require particularly careful selection, as they have a direct influence on the hygiene, safety and long-term stability of drinking water installations. What is decisive is less the material name than the specifically tested and documented material quality.

Elastomers such as EPDM and silicone have proven themselves in the drinking water sector, provided they have a valid KTW-BWGL and, where applicable, DVGW approval. Other materials are suitable only to a limited extent or exclusively for technical applications outside contact with drinking water. A standard-compliant material selection, matched to temperature, pressure and duration of use, contributes substantially to operational safety and to the permanent safeguarding of drinking water quality.

Frequently asked questions about sealing materials for contact with drinking water

Which seals are suitable for contact with drinking water?

Only seals whose material has been tested and hygienically assessed in accordance with KTW-BWGL are suitable for contact with drinking water. In many applications, a DVGW approval is additionally required, in particular in the field of drinking water installation.

Is a food-safe seal automatically suitable for drinking water?

A food approval is not sufficient for contact with drinking water. Drinking water places higher requirements on migration, long-term stability as well as odour and taste neutrality. The explicit drinking water approval is always decisive.

Why is EPDM used so frequently in the drinking water sector?

EPDM offers very good resistance to water, steam and hot water as well as a low tendency to substance migration. In tested quality, the material is suitable for numerous applications in hot and cold water installations.

Can silicone be used permanently in contact with drinking water?

Silicones suitable for drinking water are hygienically harmless and temperature-resistant. They are used above all where high flexibility or changing temperatures are required. The mechanical load capacity is lower compared with EPDM.

What role does the ageing of seals in drinking water play?

With increasing duration of use, elasticity, recovery behaviour and surface structure change. Regular inspection and planned replacement contribute substantially to the permanent safeguarding of drinking water quality.

Our rubber sheets

For industry and trade we offer a wide variety of rubber sheets.

SBR rubber sheet

Our high-quality SBR rubber sheet (styrene-butadiene rubber) is the solution for numerous industrial and commercial applications. This rubber sheet is manufactured from first-class styrene-butadiene rubber and is characterised by its outstanding physical properties.

EPDM rubber sheet

Discover the versatility and reliability of our EPDM rubber sheet, which is manufactured from ethylene-propylene-diene monomer (EPDM). This high-quality elastomer solution has been specially developed to meet the most demanding industrial and commercial applications.

NBR rubber sheet

The NBR rubber sheet is a high-quality industrial product that has been specially developed for applications requiring excellent resistance to oils, greases and various chemicals.

Viton rubber sheet

The Viton rubber sheet is a high-quality technical product that is used for a wide range of industrial applications. Manufactured from fluoro rubber (FKM), it offers outstanding properties that make it the ideal choice for extreme conditions.

FKM rubber sheet

The FKM rubber sheet is a high-quality technical product that is ideal for use in demanding industrial applications. Made from fluoro rubber (FKM), it is distinguished by a wide range of outstanding properties that make it the optimum choice for extreme operating conditions.

Silicone rubber sheet

The silicone rubber sheet is a first-class technical product that has been specially developed for applications placing high demands on temperature resistance and flexibility.

PUR rubber sheet

The PUR rubber sheet, made from high-quality polyurethane, is a technically advanced product that has been developed for applications placing the highest demands on abrasion resistance and mechanical load capacity.

Neoprene rubber sheet

The Neoprene rubber sheet, manufactured from high-quality chloroprene rubber (CR), is a versatile technical product that is ideal for a wide range of industrial and commercial applications.