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EPDM O-rings

-40 °C to 130 °C

EPDM (Ethylene Propylene Diene Monomer) is an elastomer with excellent resistance to water, steam, many dilute acids and alkalis, and atmospheric effects. Not compatible with mineral oils.

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Temperature and chemical compatibility

Temperature and chemical compatibility

Temperature range: -40 °C to +130 °C (short-term up to +150 °C).

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Typical applications: drinking water (with a suitably certified compound), steam systems (a peroxide-cured compound above approx. 130 °C), many dilute acids and alkalis, refrigeration, HVAC, brake systems (glycol-based DOT 3/4).

EPDM

Each elastomer has different mechanical and chemical properties.

EPDM — properties and applications

EPDM (ethylene-propylene-diene monomer) is an elastomer intended above all for water, steam and the outdoors. It's a material that copes where ordinary O-rings made from other rubbers age quickly — it excels in resistance to ozone, UV radiation and weathering. The typical hardness of EPDM O-rings is 70 ShA and the working temperature range is −40 to +130 °C (briefly up to +150 °C), so it covers most sanitary and heating applications.

It resists water and water vapour (for steam above approx. 130 °C, choose a peroxide-cured compound), glycol-based brake fluids (DOT 3/4), ozone, UV and weathering, as well as many acids and bases and polar solvents, extremely well. This is precisely why EPDM is the natural choice wherever NBR fails on ozone and weathering, and where you're working with water and steam media. Food-safe EPDM compounds are also used in contact with drinking water — what's decisive, though, is whether the specific compound carries the relevant certification.

EPDM's biggest limitation is clear and unchanging: it isn't suitable for mineral oils, fuels and petroleum-based lubricants. In them it swells and degrades, so never deploy it in oils or fuels — that's the most common mistake in material selection. It's likewise unsuitable for mineral brake fluids (LHM); it is only suitable for glycol-based DOT fluids. For oil applications, reach for NBR or FKM.

Typical uses of EPDM O-rings are found in water and steam circuits, in sanitary and heating (HVAC) systems, in cooling and air-conditioning lines, in glycol-based brake systems, and in outdoor seals exposed to the weather. It also sees use in solar and photovoltaic installations, where long-term resistance to UV and ozone is key. Compared with NBR it's similar in price but with the opposite media profile: where NBR excels (oils), EPDM fails, and vice versa. Choose EPDM for water and steam, DOT brake fluids and anywhere NBR isn't enough on ozone and UV — but never in oils or fuels.

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O-ring material comparison

Indicative values for a quick comparison. Temperature ranges are conservative (continuous service); for a specific medium always verify compatibility or consult a technician.

MaterialTemperature rangeMineral oilWaterAcidFuelHardness (Sh A)Relative price (vs NBR)
NBR-30 – 100 °C Excellent Limited Avoid Excellent70 Sh A1.0×
HNBR-30 – 150 °C Excellent Limited Avoid Excellent75 Sh A3.0×
FKM-20 – 200 °C Excellent Limited Excellent Excellent75 Sh A5.0×
FFKM-20 – 260 °C Excellent Excellent Excellent Excellent75 Sh A50.0×
EPDM — your selection-40 – 130 °C Unsafe Excellent Excellent Unsafe70 Sh A1.2×
VMQ-60 – 200 °C Avoid Excellent Avoid Avoid70 Sh A3.5×
PU-40 – 80 °C Excellent Limited Avoid Limited90 Sh A2.0×

Frequently asked questions about EPDM

Why should you never put an EPDM O-ring in oil?
EPDM is chemically incompatible with mineral oils, fuels and petroleum-based lubricants — in contact with them it swells markedly, softens and quickly loses its sealing ability. It's the most common mistake when swapping materials. For oils and fuels, use NBR or FKM; keep EPDM for water, steam and brake fluids.
Is EPDM suitable for drinking water and steam?
EPDM is one of the best choices for water and water vapour, and it's used in sanitary, heating and steam circuits. For contact with drinking water, however, what's decisive is whether the specific compound carries the relevant health certification — the EPDM material on its own doesn't guarantee a certificate. If you need a ring with documented drinking-water certification, contact Filip and he'll recommend a suitable compound with documentation.
Can an EPDM O-ring handle DOT brake fluid?
Yes, EPDM is the standard material for glycol-based brake fluids (DOT 3, DOT 4) — this is exactly where it's at home and where NBR or FKM would fail. Note that this doesn't apply to mineral brake fluids (LHM), where EPDM is, conversely, unsuitable. For a specific fluid, always check the type of base (glycol vs. mineral oil).

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