Rubber Gaskets

Last updated: April 2026

A rubber gasket is an elastomer flange gasket cut from sheet rubber — EPDM, nitrile (NBR), neoprene (CR), Viton (FKM), silicone, or natural rubber. Rubber gaskets are the low-cost, low-pressure workhorse for water, air, and mild-chemical flange service, with each elastomer chosen to match the media, temperature, and compliance requirement.

GritGasket cuts rubber gaskets to any flange pattern — AS 2129, ASME B16.21, BS 10, or custom — from premium Australian and imported sheet. WRAS / AS 4020 potable-water grades, FDA food-contact grades, and high-spec Viton and silicone grades all stocked and shipped across Australia and New Zealand.

What Is a Rubber Gasket?

A rubber gasket is a cut or moulded elastomer sealing element used between two flanges, plate surfaces, or housings. Rubber is soft enough to conform to surface irregularities at low bolt load, which makes it the right choice wherever the service is low-pressure, the flanges are not ideal, and the media is compatible with at least one common elastomer.

Six elastomer families cover virtually every rubber-gasket application:

Elastomer	Temp range	Best for	Avoid
EPDM	−40 to +120 °C	Potable water, steam (LP), HVAC, weathering	Oil, fuel, hydrocarbons
Nitrile (NBR)	−30 to +110 °C	Oil, fuel, hydraulic, compressed air	Ozone, weathering, polar solvents
Neoprene (CR)	−30 to +100 °C	General-purpose, weather-exposed, refrigerants	Strong acids, esters
Viton® (FKM)	−20 to +200 °C	Aggressive chemicals, high temp, fuel, ozone	Steam, amines, ketones
Silicone (VMQ)	−55 to +230 °C	Dry heat, food-contact, high temp air	Steam (hydrolysis), oil
Natural rubber (NR)	−30 to +70 °C	Abrasive slurries, mining duct flanges	Oil, fuel, ozone

Which Rubber for Which Job?

Water, steam, HVAC → EPDM

EPDM is the default rubber for any water or hot-water duty. Potable water (WRAS/AS 4020), chilled water, cooling towers, low-pressure steam (below ~130 °C), and HVAC flanged coils all use EPDM. Do not put EPDM in oil — it swells aggressively.

Oil, fuel, hydraulic → Nitrile (NBR)

Nitrile resists mineral oil, petroleum fuel, lubricants, and hydraulic fluid. It is the standard rubber for diesel generator sets, compressed-air flanges, and fuel-line gaskets. 70 Shore A is the workhorse hardness.

Aggressive chemicals, high temp → Viton (FKM)

Viton handles concentrated acids, hydrocarbons, and temperatures to 200 °C. It is more expensive than other elastomers but often the only viable rubber for solvent-service, aromatic hydrocarbons, or hot-oil flanges. A common upgrade when nitrile fails on temperature.

Weather exposure, refrigerants → Neoprene (CR)

Neoprene bridges oil resistance (not as good as NBR) and weather resistance (not as good as EPDM) — useful on outdoor, general-purpose flanges, refrigerant lines, and marine duty.

Dry heat, food-contact → Silicone

Silicone tolerates +230 °C and is FDA-compliant for food-contact. Do not use in steam (hydrolysis) or pressurised hot water. Common on ovens, food-processing plant, and electrical/medical enclosures.

Hardness and Thickness

Standard stock hardness is 65 Shore A (soft, conforms easily) and 70–80 Shore A (firmer, handles higher pressure). Thicker gaskets tolerate worse flanges but need more bolt load to seat:

1.5 mm — flat, machined flange faces, low pressure.
3.0 mm — general-purpose raised-face; the most commonly specified thickness.
5–6 mm — uneven or corroded flanges.
10 mm+ — patched flanges, mining slurry duty, anti-vibration duty.

Where Are Rubber Gaskets Used?

Water treatment — potable, waste, and desalination plant flanges (EPDM, WRAS).
HVAC & building services — chiller and coil flanges, pump suction lines (EPDM).
Fuel and hydraulic systems — diesel, LP gas, compressed air (NBR).
Food & pharma — sanitary flanges, CIP lines (FDA EPDM or silicone).
Mining — slurry ducts, abrasive lines (natural rubber or NBR).
Chemical plant — dilute acid/alkali transfer lines (Viton).

Installation Notes

Rubber gaskets require low seating stress (5–15 MPa) — do not over-tighten. Follow a cross-pattern bolt-up and tighten only until the gasket bulges slightly at the flange OD. Over-compression extrudes the rubber out of the joint and causes leakage within weeks. Our bolt torque calculator handles low-stress soft-gasket sizing.

Stocked Rubber Gaskets

RUB-EPDM-65

Nitrile (NBR) Rubber Gasket (70 Shore A)

RUB-NBR-70

Frequently Asked Questions

There is no single "best" rubber — each elastomer suits different media. EPDM is the default for water, hot water, steam (LP), and HVAC. Nitrile (NBR) is best for oil, fuel, and hydraulic service. Viton handles aggressive chemicals and high temperature (up to 200 °C). Silicone is for dry heat and food-contact. Neoprene is a general-purpose middle ground. Natural rubber is reserved for abrasive slurry duty. Start with the media, then pick the elastomer that tolerates it at your service temperature.

Yes, but only on low-pressure steam. EPDM handles saturated steam up to around 130 °C (about 2 bar g) continuously. Higher-pressure steam needs a flexible graphite, spiral wound, or kammprofile gasket. Do not use nitrile, neoprene, or Viton on steam — they hydrolyse and fail. Silicone also hydrolyses in pressurised steam and must be avoided.

Standard hardness is 65 or 70 Shore A. 65 Shore A is softer — conforms better to imperfect flange faces, seals at lower bolt load. 70 Shore A is firmer — handles higher pressures without extruding out of the joint. For flat, machined flanges specify 65. For raised-face Class 150 pipe flanges specify 70. For very uneven or patched flanges, thicker sheet at 60 Shore A works best.

Yes — WRAS-approved and AS/NZS 4020 certified EPDM grades are the Australian standard for potable-water flange gaskets. We stock certified peroxide-cured EPDM (AS 4020 preferred over sulphur-cured for taste and odour neutrality). Always ask for the compliance certificate when specifying potable-water service.

Leaks on rubber gaskets usually come from one of three causes: (1) wrong elastomer for the media — check chemical compatibility, (2) over-tightening that extruded the rubber out of the joint — back off to target torque and replace, or (3) the gasket has taken compression set and lost elasticity — replace on any re-torque or disassembly cycle. Rubber gaskets are single-use on any critical service.

Learn More

Sources

AS/NZS 4020 — Testing of products for use in contact with drinking water
ASME B16.21 — Nonmetallic Flat Gaskets for Pipe Flanges
ASTM D2000 — Rubber products in automotive applications (elastomer classification)
FDA 21 CFR 177.2600 — Rubber articles intended for repeated food contact