EPDM Chemical Compatibility Chart
EPDM is one of the most common elastomers in water and chemical valve service, but it is not compatible with every chemical. This chart is for initial screening — final valve selection must account for concentration, temperature, pressure, mechanical stress, cycle frequency, off-gassing, and the exact wetted part.
| Chemical / Service | EPDM Compatibility | Practical Spec Note |
|---|---|---|
| Potable water | Good | Common EPDM service. Confirm temperature and approvals. |
| Hot water / steam | Good / Conditional | Strong EPDM category, but verify pressure and temperature limits. |
| Caustic soda / sodium hydroxide | Good / Conditional | Strong in many aqueous caustic services; higher temperatures tighten the envelope. |
| Sodium hypochlorite, low concentration | Conditional | Must verify concentration, temperature, off-gassing, and valve design. |
| Sodium hypochlorite, 12.5% | Limited / Conditional | Do not treat EPDM as automatically approved. Consider composite diaphragm or manufacturer-specific hypo configuration. |
| Ferric chloride | Good / Conditional | Common water-treatment chemical; verify concentration and temperature. |
| Ferric sulfate | Good | Often favorable in aqueous coagulant service. |
| Fluosilicic acid | Conditional | Common fluoride chemical; temperature matters. |
| Phosphoric acid | Good / Conditional | Often usable depending on concentration and temperature. |
| Hydrochloric acid, dilute | Good / Conditional | Higher concentrations and temperature reduce margin. |
| Sulfuric acid, dilute | Good | 10% sulfuric acid is a favorable EPDM screening category. |
| Sulfuric acid, concentrated | Not Recommended | Higher concentrations move into limited or no-resistance territory. |
| Fuel oil | Not Recommended | EPDM is a poor fit for hydrocarbon/oil service. |
| Heptane / hexane | Not Recommended | Hydrocarbon swelling risk. |
| Kerosene | Not Recommended | Hydrocarbon service usually points away from EPDM. |
| Lubricating oils | Not Recommended | Use another elastomer family, often FKM depending on full conditions. |
| Natural gas | Not Recommended | EPDM is generally not the hydrocarbon/gas elastomer choice. |
Do not search the chemical name and stop there. EPDM compatibility depends on six things: chemical name, concentration, operating temperature, pressure, valve type, and which elastomer part is exposed.
A valve can have the right body material and the wrong elastomer. A PVC, CPVC, PP, or PVDF valve body may survive the chemical while the EPDM seal, O-ring, or diaphragm fails first.
| Material | Best Fit | Weak Spot | Common Valve Use |
|---|---|---|---|
| EPDM | Water, caustic, many aqueous chemicals | Oils, fuels, hydrocarbons, many solvents | O-rings, seals, diaphragms |
| FKM | Hydrocarbons, oils, fuels, many solvents | Steam, hot water, strong alkalis, some oxidizers depending on compound | O-rings, seats, seals |
| PTFE | Broad chemical resistance, liners, seats, aggressive chemicals | Flexibility, permeation, mechanical support | Seats, liners, diaphragm wetted layer |
| EPDM/PVDF/PTFE composite | Sodium hypochlorite/off-gassing diaphragm service | Must match valve design/manufacturer | Diaphragm valves |
Choosing EPDM Because the Valve Body Is Compatible
A PVC or PVDF body can survive while the elastomer fails. Body material and elastomer material are separate decisions.
Treating Chemical Name as Enough Information
Sodium hypochlorite at 3%, 12.5%, ambient temperature, and elevated temperature are not the same service.
Ignoring Temperature
Temperature often turns a "good" material into a conditional or failed material.
Forgetting Off-Gassing
In sodium hypochlorite and similar media, trapped chemical in a closed valve cavity can create pressure and crystallization problems. Venting and valve design need review before replacement.
Frequently Asked Questions
What is EPDM compatible with?
EPDM is generally strong in water, steam, caustic solutions, many aqueous salts, dilute acids, and many water-treatment chemicals. It is generally weak in petroleum oils, fuels, hydrocarbons, aromatic solvents, chlorinated solvents, and many organic solvents.
How should I use this chart?
This chart is for initial screening only. Final valve selection should account for concentration, temperature, pressure, mechanical stress, cycle frequency, off-gassing, and the exact wetted part: seat, seal, O-ring, diaphragm, liner, or body.
Is EPDM safe for sodium hypochlorite valve service?
Sometimes, but not automatically. EPDM can be used in some sodium hypochlorite services, but the concentration, temperature, off-gassing behavior, and valve construction determine whether it is the right choice. Asahi/America describes a sodium hypochlorite diaphragm valve using a three-layer EPDM/PVDF/PTFE diaphragm with a gas barrier for aggressive off-gassing service.
Before you replace the valve again
If the same chemical valve keeps failing, the valve brand may not be the problem. Send LibertyCES the chemical name, concentration, temperature, pressure, and valve type.