EPDM O-rings

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, 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 only applies to glycol-based DOT. 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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