EPDM O-Rings
The preferred sealing material for water, steam, HVAC systems and outdoor applications requiring ozone and weathering resistance.
Overview
EPDM (Ethylene Propylene Diene Monomer) is the leading elastomer for water, steam and weather-exposed sealing applications. Its fully saturated polymer backbone provides outstanding resistance to ozone, UV radiation and atmospheric aging — properties that make it essential for outdoor, HVAC and water treatment applications where NBR and FKM deteriorate rapidly.
With a service temperature range of -50°C to +150°C and excellent resistance to hot water and saturated steam up to approximately 4–5 bar, EPDM is specified across heating systems, water treatment plants, food processing equipment and building HVAC installations. Peroxide-cured EPDM compounds achieve compression set (ASTM D395 Method B, 70 h/150°C) ≤ 20%, outperforming sulfur-cured grades for long-term static sealing.
FDA 21 CFR §177.2600 compliant grades are available for direct food contact. NSF/ANSI 61 approved compounds are available for potable water system components. For UK water systems, WRAS-approved EPDM grades are also stocked.
The critical limitation of EPDM is its incompatibility with petroleum oils and hydrocarbon fuels. Immersion testing per ASTM D471 in IRM 903 oil at 100°C shows volume swell exceeding 40%, making EPDM unsuitable for any mineral oil hydraulic system. For environments where both water and oil are present, contact our engineering team for compound selection guidance.
Lead time: 7–15 days standard; 3–5 days for stocked compounds. MOQ: 1 piece. ISO 9001 certified production. RoHS and REACH compliant.
EPDM's molecular structure is a terpolymer of ethylene, propylene, and a non-conjugated diene third monomer — most commonly ethylidene norbornene (ENB) or dicyclopentadiene (DCPD). The ethylene and propylene units form a fully saturated backbone with no carbon-carbon double bonds, which is the origin of its exceptional ozone and UV resistance. The diene component introduces pendant unsaturation for vulcanization while preserving backbone saturation. ENB content typically ranges from 4–8% by weight and directly affects cure rate and crosslink density: higher ENB accelerates peroxide vulcanization and increases modulus but can reduce heat aging resistance. Peroxide curing creates carbon-carbon crosslinks that are thermally stable to over 180°C, whereas sulfur-cured EPDM forms polysulfidic bonds that begin to revert above 130°C — explaining why peroxide-cured grades achieve ≤ 20% compression set at 150°C while sulfur-cured grades only achieve ≤ 25%.
Quantified comparative data illustrates EPDM's unique position. In ozone resistance testing (ASTM D1171, 50 pphm ozone, 40°C, 20% strain), EPDM shows no cracking after 1000 hours, while NBR fails within 24–48 hours and CR shows moderate cracking after 200–400 hours. In tensile strength, EPDM (10–18 MPa) significantly outperforms VMQ silicone (5–10 MPa) by 50–100%, making EPDM the better choice for pressurized outdoor seals where mechanical robustness matters. In compression set at 150°C (ASTM D395 Method B, 70 h), peroxide-cured EPDM achieves ≤ 20% versus VMQ's ≤ 30% at 175°C — when normalized to equivalent temperature, EPDM holds sealing force more effectively in hot water and steam service. Specific gravity of 0.86–0.87 makes EPDM the lightest common elastomer; it actually floats in water, which is useful for visual identification in submerged applications.
A practical decision tree for EPDM selection: if your application is a potable water valve seal, specify NSF/ANSI 61 certified 70 Shore A black EPDM with peroxide cure — the peroxide cure eliminates extractable sulfur residues. If your application is a steam autoclave seal at 135°C and 3 bar, specify peroxide-cured EPDM at 80 Shore A for improved compression set resistance under sustained load. If your application is an outdoor electrical enclosure gasket in a coastal environment, specify 60 Shore A EPDM for maximum conformability to flange irregularities, with UV stabilizer package — the softer grade accommodates thermal expansion mismatches between metal and plastic housings. If your application involves CIP (clean-in-place) protocols in food processing with caustic soda and nitric acid cycles, specify FDA-grade peroxide-cured EPDM and verify compatibility with your specific cleaning chemical concentrations. If your application sees even trace petroleum oil contact, do not use EPDM — specify NBR, HNBR, or FKM instead.
Storage recommendations for EPDM are straightforward but important. EPDM's saturated backbone makes it naturally resistant to ozone cracking during storage, unlike NBR which degrades even at ambient ozone levels. Store EPDM O-rings in a cool, dry environment below 25°C, away from direct sunlight (UV can cause surface oxidation and slight hardening over years), and away from petroleum products or solvents. Peroxide-cured EPDM has a shelf life of approximately 7–10 years under ideal conditions; sulfur-cured grades are stable for 5–7 years. EPDM is hygroscopic to a minor degree — prolonged storage in humid environments (>70% RH) can cause surface bloom of processing aids, which wipes clean and does not affect performance. A common engineering error is selecting EPDM for water-glycol hydraulic fluid (HFC) seals without verification: while EPDM resists water, some glycol ether additives in HFC fluids can cause moderate swell; always request ASTM D471 immersion data in the specific HFC fluid formulation before specifying EPDM.
Material Properties
| Temperature Range | -50°C to +150°C (-58°F to +302°F) |
| Hardness Range | 40–90 Shore A (ASTM D2240) |
| Tensile Strength | 10–18 MPa (ASTM D412) |
| Elongation at Break | 150–400% (ASTM D412) |
| Compression Set (70 h/150°C) | ≤ 20% peroxide-cured; ≤ 25% sulfur-cured (ASTM D395 Method B) |
| Specific Gravity | 0.86–0.87 (lightest common elastomer — floats in water) |
| Low-Temperature Flexibility (TR10) | -45°C to -50°C (ASTM D1329) |
| Color (standard) | Black |
| Compliance | FDA 21 CFR §177.2600; NSF/ANSI 61 (potable water grades); WRAS available |
Typical Applications
Water Treatment
Pipeline flange seals, valve O-rings and pump seals in potable water and wastewater systems. NSF 61 certified grades available.
HVAC
Heating system seals, glycol cooling circuit O-rings and air handling unit seals where condensation and ozone exposure are constant.
Food & Beverage
FDA-grade seals for food processing equipment, dairy systems, CIP circuits and beverage dispensing in contact with aqueous cleaning agents.
Steam Systems
Saturated steam seals to ~150°C and 4–5 bar in autoclaves, steam-jacketed piping and low-pressure condensate return lines.
Outdoor Equipment
Weather-exposed seals, outdoor electrical enclosure seals and solar panel mounting hardware requiring multi-year ozone and UV resistance.
Chemical Compatibility Summary
Compatible With
- - Hot water and steam
- - Polar solvents
- - Glycol-based brake fluids
- - Skydrol
- - Dilute acids and alkalis
Incompatible With
- - Mineral oils
- - Hydrocarbon fuels
- - Aromatic hydrocarbons
- - Chlorinated solvents
- - Turpentine
Compare Nearby Materials
Further Reading
EPDM vs Silicone
The practical tradeoff between steam resistance, low temperature, and clean static sealing.
Read articleBest Material for Steam
Why peroxide-cured EPDM is usually the starting point for steam duty.
Read articleKey Advantages
Best Choice for Water and Steam
EPDM performs reliably in hot water, saturated steam to 150°C and glycol-based systems where NBR swells excessively and FKM lacks hydrolysis resistance at elevated temperatures.
Outstanding Weather Resistance
Saturated backbone resists ozone cracking and UV degradation for 10+ years of outdoor service — significantly outperforming NBR, which cracks within months in ozone-rich environments.
Food and Potable Water Grades Available
FDA 21 CFR §177.2600 and NSF/ANSI 61 certified EPDM compounds available for food processing, beverage systems and clean water applications with full lot traceability.
Broad Low-Temperature Flexibility
TR10 retraction temperature of -45°C to -50°C (ASTM D1329) ensures reliable cold-start sealing in outdoor, refrigeration-adjacent and variable-temperature systems.
Lightest Common Elastomer with Positive Water Identification
With a specific gravity of 0.86–0.87, EPDM is the only common O-ring material that floats in water. This provides immediate visual verification during installation or failure analysis in water systems — if the retrieved seal sinks, it is not EPDM. This property, combined with 50–100% higher tensile strength than VMQ silicone, makes EPDM the mechanically robust choice for pressurized water and steam applications.
Superior CIP and SIP Chemical Resistance for Food-Pharma Service
Peroxide-cured FDA-grade EPDM withstands standard CIP cycles: 1–4% NaOH at 80°C, 1–2% HNO₃ at 70°C, and peracetic acid (PAA) up to 0.2% — with volume changes under 10% and tensile retention above 80% after 1000 cycles in accelerated testing. Sulfur-cured grades show 15–25% higher swell in caustic due to extractable sulfur residues. For pharmaceutical SIP (steam-in-place) protocols, peroxide-cured EPDM maintains compression set ≤ 25% after 200+ steam sterilization cycles at 135°C.
Frequently Asked Questions - EPDM
Can EPDM O-rings handle steam?
Yes. EPDM is one of the best elastomers for saturated steam service up to approximately 150°C and 4–5 bar. Specify peroxide-cured EPDM for steam applications — it achieves compression set ≤ 20% (ASTM D395 Method B, 70 h/150°C), compared to ≤ 25% for sulfur-cured grades. For superheated steam above 150°C or pressures above 10 bar, PTFE or metal seals are required.
Is EPDM safe for drinking water applications?
Yes. EPDM O-rings are available in NSF/ANSI 61 certified compounds for potable water system components including valves, meters and fittings. For food contact applications, FDA 21 CFR §177.2600 compliant grades are available. Always request the compound-specific compliance certificate — not all EPDM formulations meet these standards.
Why can EPDM not be used with hydraulic oil?
EPDM has poor resistance to petroleum-based oils and fuels. ASTM D471 immersion testing in IRM 903 reference oil at 100°C shows volume swell typically exceeding 40%, causing rapid softening and loss of sealing force. For oil-resistant sealing, use NBR (to 120°C) or HNBR (to 150°C) instead.
How does EPDM compare to silicone for outdoor sealing?
Both EPDM and VMQ (silicone) resist ozone and UV, but they differ in mechanical performance. EPDM has tensile strength of 10–18 MPa versus VMQ's 4–10 MPa, making EPDM significantly more durable in dynamic or high-pressure outdoor sealing. VMQ is preferred for extreme temperatures (-60°C to +200°C) or where low compression set at elevated temperatures is critical. For standard outdoor enclosures and HVAC seals, EPDM is the cost-effective choice.
Is EPDM compatible with CIP cleaning chemicals in food processing?
Yes, for most common CIP agents. FDA-grade EPDM resists sodium hydroxide (caustic soda) at standard cleaning concentrations (1–4%), phosphoric acid, and peracetic acid (PAA) at concentrations up to 0.2%. Nitric acid above 5% causes volume swell and is not recommended. Always verify against your specific cleaning protocol, and request ASTM D471 immersion data for your cleaning agents if operating at elevated temperatures.
What is EPDM's low-temperature performance?
Standard EPDM remains flexible to approximately -45°C to -50°C as measured by TR10 retraction temperature (ASTM D1329). This is superior to FKM (-20°C to -30°C) and makes EPDM suitable for outdoor heating systems and refrigerant-adjacent equipment in cold climates. For applications below -50°C, silicone (VMQ) or specialty low-temperature EPDM compounds are required.
What is the MOQ and lead time for EPDM O-rings?
MOQ is 1 piece for stocked AS568 and ISO 3601 sizes in standard 70 Shore A black EPDM. Lead time is 3–5 business days for stocked compounds and 7–15 days for custom sizes or specialty grades (FDA, NSF, WRAS). Custom cross-sections or non-standard sizes may require 3–4 weeks. Volume pricing is available from 100 pieces with blanket order programs for annual commitments.
Do EPDM compounds have IATF 16949 or WRAS certifications for specific industries?
Yes, EPDM compounds are available from IATF 16949-certified production lines for automotive coolant and HVAC applications, with full PPAP and material test report documentation. For UK water industry applications, WRAS (Water Regulations Advisory Scheme) approved EPDM compounds are stocked for AS568 and metric sizes — each WRAS approval is compound-specific and includes the approval number on the CoC. For North American potable water, NSF/ANSI 61 certification is standard. Specify the required certification (WRAS, NSF, KTW, ACS, or specific OEM material specification) when ordering, as not all stocked compounds carry every approval.
How do you guarantee batch consistency for EPDM, especially for FDA and NSF grades?
Batch consistency for EPDM is controlled through a documented quality plan: (1) Polymer lot testing — Mooney viscosity, ethylene content (45–55% by weight for standard grades), and ENB level are verified against incoming specifications. (2) Compounding — carbon black type (N550 or N774 for general grades, N990 for low-compression-set grades), paraffinic oil plasticizer, and peroxide curative are weighed to ±0.2%. (3) In-process testing — every batch is tested on MDR for scorch safety (tS2 > 3 min) and cure rate (t90); press-cured slabs are tested for hardness (±3 Shore A), specific gravity (±0.02), tensile (±10%), and elongation (±15%). (4) Certification batch testing — FDA and NSF compounds additionally undergo extractables testing (FDA 21 CFR §177.2600 aqueous and n-hexane extracts) and NSF 61 normalization testing on a representative batch basis. Lot-specific CoCs include all test data and compound formulation reference.
Can EPDM O-rings from different suppliers be used interchangeably?
Dimensionally, AS568 and ISO 3601 EPDM O-rings are interchangeable across reputable suppliers. Material equivalence requires verifying three parameters: cure system (peroxide vs sulfur — peroxide-cured has better heat resistance and lower extractables), ethylene content (45–55% is standard; higher ethylene improves low-temperature flexibility but reduces oil resistance, which is irrelevant for EPDM's water/steam niche), and third monomer type (ENB vs DCPD — ENB is standard for peroxide cure). Compression set can vary by 3–8 percentage points between suppliers even within the same hardness and cure system. For critical steam or autoclave applications, request ASTM D395 Method B compression set data at 150°C from both suppliers and confirm the values are within your design margin before switching. FDA and NSF certifications are supplier-specific and cannot be transferred — a new supplier must have their own compound-specific certifications.
What color coding conventions are used for EPDM O-rings?
Black is the standard color for industrial EPDM O-rings. Blue is widely used for NSF/ANSI 61 potable water grades and FDA food-contact grades as a visual differentiator from industrial black compounds. White or off-white EPDM is sometimes specified for food processing where carbon black pigment is undesirable for aesthetic or detectability reasons. Green may denote sulfur-cured EPDM in some supplier color systems, while peroxide-cured remains black or blue. Custom colors (red, yellow, orange) are available with 1–2 week additional lead time and minimum order quantities of 500–1000 pieces. Because EPDM is the lightest common elastomer (specific gravity 0.86–0.87, floating in water), color plus float-test provides rapid field identification in water system maintenance.
What is the sustainability and recyclability profile of EPDM?
EPDM has a favorable sustainability position among elastomers. The polymer is produced from ethylene and propylene — commodity petrochemicals with established recycling infrastructure for the monomers. EPDM's long service life in outdoor and water applications (10–20 years for building envelope seals, 5–10 years for potable water valves) reduces replacement frequency and associated material consumption. Post-industrial EPDM scrap (flash, rejected parts) is ground and used in roofing membranes, playground surfaces, and automotive underbody coatings — achieving recycling rates of 20–30% in well-managed facilities. EPDM is REACH and RoHS compliant. Bio-based EPDM grades using sugarcane-derived ethylene are commercially available and offer 40–70% renewable carbon content for customers with net-zero targets. All our EPDM compounds are free of heavy metals, phthalates, and intentionally added PFAS.