Valve Seat Material Guide: EPDM vs. Buna-N vs. Viton vs. PTFE
The seat is what actually seals a valve, and it sets the chemical and temperature limits — not the body. Choosing the wrong elastomer is the most common cause of premature valve failure. This guide compares the four seat/seal materials you'll see most often on butterfly, ball, and check valves.
Quick compatibility table
General guidance — always verify against a chemical compatibility chart for your exact media and concentration.
| Material | Great for | Avoid with | Typical temp range |
|---|---|---|---|
| EPDM | Water, hot water, steam, dilute acids & bases, alcohols, ketones | Petroleum oils, fuels, hydrocarbons | ~ -40°F to 300°F |
| Buna-N (Nitrile/NBR) | Petroleum oils, fuels, hydraulic fluid, air, natural gas | Ozone/weather, strong acids, ketones | ~ -30°F to 250°F |
| Viton (FKM) | Aggressive chemicals, oils, fuels, high temperature | Hot water/steam, ketones, amines | ~ -15°F to 400°F |
| PTFE | Near-universal chemical resistance; standard ball-valve seat | (Firm, not elastic — less forgiving on dirty media) | ~ -50°F to 450°F |
How to choose
Water, HVAC, steam? EPDM. Oil, fuel, or air? Buna-N. Hot and chemically aggressive? Viton. Broad chemical service or a ball valve? PTFE. The classic mistake is using EPDM on a petroleum line or Buna-N on a steam line — both swell or harden quickly.
Where you'll see each
Most resilient-seated butterfly valves use EPDM (water/HVAC) or Buna-N (oil/air) seats. Ball valves typically use PTFE seats for broad chemical service. Check valves vary by type and media.
Related
Apply this when selecting a butterfly valve or reviewing the valve body material guide. Not sure which seat suits your chemical? Contact us with your media and temperature and we'll confirm.