How to Choose the Right Seal Material for Drinking Water Applications

Selecting the right seal material is essential for ensuring the safety, reliability and long-term performance of drinking water systems. From water treatment plants and distribution networks to pumps, valves and plumbing equipment, seals must prevent leaks while meeting strict requirements for materials in contact with potable water.

However, not all sealing materials are suitable for drinking water applications. Factors such as regulatory compliance, water temperature, pressure, chemical exposure and service life must all be considered when choosing the right solution.

Here are the key considerations when selecting seal materials for drinking water applications.

 

1. Prioritise Drinking Water Compliance

The first step in selecting a seal material is confirming that it is approved for contact with drinking water in the intended market.

Materials used in potable water systems must not adversely affect water quality, introduce harmful substances or cause unacceptable changes to taste, odour or appearance.

Requirements vary depending on the country and application. In the UK, relevant considerations include the Water Supply (Water Fittings) Regulations and applicable requirements under the Water Regulations Approval Scheme (WRAS). Other markets have their own approval frameworks, such as NSF/ANSI/CAN 61 in North America and applicable European national requirements.

It is important to note that approval of a raw material does not automatically mean that every finished seal made from it is approved. Always check that the specific compound, product and intended conditions of use meet the relevant requirements.

 

2. Understand the Operating Conditions

Even an approved material may not perform reliably if it is unsuitable for the application's operating environment.

Before selecting a seal, consider the following factors:

-- Temperature: Will the seal be exposed to cold mains water, warm water or elevated temperatures during cleaning or disinfection?

-- Pressure: Must the seal withstand continuous system pressure, pressure fluctuations or occasional pressure spikes?

-- Movement: Is the seal used in a static connection, such as a pipe joint, or a dynamic application, such as a pump or valve?

-- Chemical exposure: Could the seal come into contact with chlorine, chloramines, cleaning agents or other water-treatment chemicals?

-- Service life: How long must the seal operate reliably, and how accessible is it for inspection or replacement?

Understanding these conditions helps narrow down the available materials and reduces the risk of premature failure, leakage or unnecessary maintenance.

 

3. Common Seal Materials for Drinking Water and WRAS-Approved Applications

Several materials are used in drinking water applications, each offering different performance benefits.

EPDM

EPDM is one of the most widely used materials for drinking water sealing applications due to its excellent resistance to water, hot water and weathering. It is commonly used in O-rings, gaskets, valves and water distribution systems.

NBR (Nitrile)

NBR offers good resistance to oils and greases and can be suitable for certain potable water applications when the correct approved compound is selected. Performance and approvals vary significantly between grades.

Silicone

Silicone provides excellent flexibility and performs well across a wide temperature range. It is often selected for applications where elasticity and temperature resistance are key requirements.

PTFE

PTFE offers outstanding chemical resistance and low friction characteristics, making it suitable for specialist water handling applications. Because it is less elastic than rubber materials, seal design is especially important.

Important: Always verify that the specific compound and finished seal meet the relevant drinking water approval requirements for the intended market and operating conditions.

 

The table below provides a quick comparison of common seal materials used in drinking water applications.

Seal Material	Typical Drinking Water Applications	Key Advantages	Key Considerations
EPDM	Pipe fittings, O-rings, valves, pumps and water distribution systems	Excellent water resistance; good hot water and weathering resistance	Generally unsuitable for mineral oils and petroleum-based fluids. Confirm disinfectant compatibility and potable water approval.
NBR (Nitrile)	Selected pump and valve seals where oil or grease contact is possible	Good oil and grease resistance; good mechanical properties in suitable grades	Standard compounds may not be approved for drinking water. Check temperature limits and long-term water resistance.
Silicone	Selected water-handling equipment, specialist fittings and applications requiring flexibility	Good flexibility and a wide operating temperature range	Can have lower tear and abrasion resistance than some alternatives. Verify suitability for pressure, movement and the specific water conditions.
PTFE	Valve seats, pump seals and specialist sealing systems	Excellent chemical resistance; low friction; broad temperature capability	Limited elasticity means seal design is critical. Installation, loading and the complete product's compliance must be assessed.

 

4. Consider the Effects of Water Treatment Chemicals

Drinking water systems may expose seals to disinfectants and other treatment chemicals. Chlorine and chloramines, for example, can affect the long-term performance of some elastomer compounds.

The impact depends on factors such as chemical concentration, temperature, exposure duration and the material formulation.

A seal that performs well in untreated water may therefore behave differently in a system with higher disinfectant levels or frequent chemical cleaning.

When evaluating materials, consider the full range of expected exposure conditions rather than relying on general chemical resistance charts alone. For critical applications, seek compound-specific compatibility data and, where necessary, specialist testing.

 

5. Check Temperature and Pressure Requirements

Temperature and pressure can significantly influence seal performance.

Higher temperatures can accelerate ageing, while pressure can cause deformation, extrusion or other forms of seal damage if the material and design are unsuitable.

For example, a seal used in a cold-water distribution network may have very different requirements from one installed in hot-water equipment or a pump operating continuously under pressure.

It is also important to consider how these factors interact. A material that performs well at moderate temperatures may have a shorter service life when exposed to elevated temperatures and sustained mechanical stress.

Always assess the material alongside the seal design, gland dimensions, mating surfaces and operating conditions.

 

6. Look Beyond the Material Name

Choosing a material based on its generic description alone can be misleading. Two compounds made from the same base polymer may have significantly different properties because of their formulation, additives and manufacturing processes.

For drinking water applications, consider:

• Compound-specific approvals: Confirm that the exact grade meets the required potable water standards.
• Mechanical properties: Check hardness, elasticity, compression set and resistance to wear.
• Dimensional stability: Ensure the material maintains an effective seal under the expected conditions.
• Traceability and quality: Look for appropriate documentation and consistent manufacturing controls.
• Application suitability: Confirm that the complete seal design is suitable for the equipment and installation.

Working with a knowledgeable sealing supplier can help identify the most appropriate combination of material, design and compliance documentation.

 

7. Balance Initial Cost with Long-Term Performance

The lowest-cost seal is not necessarily the most economical option over its service life.

Premature seal failure can result in water leakage, equipment downtime, replacement costs and additional maintenance. In some applications, it can also create hygiene or compliance concerns.

Selecting the right material from the outset can help extend service life, improve system reliability and reduce the total cost of ownership.

Consider the expected operating life, consequences of failure, ease of replacement and maintenance requirements when comparing solutions.

 

To sum up…

Selecting a seal material for drinking water applications requires more than identifying a suitable rubber or polymer. Compliance, temperature, pressure, chemical exposure, mechanical performance and long-term reliability must all be considered together.

EPDM is a common choice for many potable water applications, while NBR, silicone and PTFE may be appropriate in specific circumstances. The right solution will always depend on the operating environment and the requirements of the finished sealing product.

At M Seals, we understand that reliable sealing starts with selecting the right material for the application. Our team can help you assess your operating requirements, identify suitable sealing solutions and find the right balance between performance, compliance and service life.

Need help choosing a seal for a drinking water application? Contact M Seals for technical advice.