Although it may seem like a small detail, the valve’s O-ring material is very important. The material can determine the temperature tolerance of the seal. It also gives the seal some chemical resistance, and some types of rubber are compatible with different fluids. Two common materials for true union ball valves are Viton and EPDM.

Viton (pictured to the right) is a synthetic rubber with high chemical and temperature resistance. EPDM stands for Ethylene Propylene Diene Monomer and has its own set of properties that make it a very popular O-ring material. When comparing Viton to EPDM, several factors must be considered: temperature tolerance, chemical compatibility, and cost. Read on for the full comparison.

EPDM rubber seals
EPDM rubber (EPDM rubber) is a complex and inexpensive rubber with a wide range of uses. It is usually used for roof waterproofing because EPDM seals well. It is also a common material for freezer seals because it is an insulator and has excellent low temperature resistance. Specifically, EPDM operates effectively in the temperature range of -49F to 293F (-45C to 145C), making it ideal for applications at any temperature.

While many rubbers are high temperature resistant, only a few can handle lower temperatures like EPDM. This makes it the first choice for anyone trying to seal in cold environments or with cold materials. True Union Ball Valves with EPDM Sealed O-Rings Typical applications for EPDM include electrical insulation, pool linings, plumbing, solar panel collectors, O-rings, and more.

In addition to greater temperature tolerance, EPDM has a broad chemical resistance. These include hot water, steam, detergents, caustic potash solutions, sodium hydroxide solutions, silicone oil/grease, and many other diluted acids and chemicals. It is not suitable for use with mineral oil products such as lubricating oils, oils or fuels. For specific chemical compatibility of EPDM, click here. These impressive properties, combined with its low price, make EPDM a very popular sealing material.

Viton seals
Viton is a synthetic rubber and fluoropolymer elastomer. “Fluoropolymer” means that this material has a high resistance to solvents, acids and bases. The word “elastomer” is basically interchangeable with “rubber”. We won’t discuss the difference between elastomer and rubber here, but we will discuss what makes Viton so special. The material is often characterized by a green or brown color, but what really sets it apart is its density. Viton’s density is significantly higher than most types of rubber, making the Viton seal one of the strongest.

Viton has a wide temperature tolerance range from -4F to 410F (-20C to 210C). The high temperatures that Viton can withstand makes it ideal for high temperature applications. Viton is commonly used in O-rings, chemical resistant gloves and other molded or extruded products. O-rings made from Viton are great for scuba diving, car engines and various valves.

When it comes to chemical resistance, Viton is unmatched. It resists corrosion from a wider variety of fluids and chemicals than any non-fluorinated elastomer. Unlike EPDM, Viton is compatible with oils, fuels, lubricants and most inorganic acids. It is also extremely resistant to compression, atmospheric oxidation, sunlight, weathering, oxygenated motor fuels, aromatics, fungi, mold, and more. It is also inherently more resistant to burning than most other rubbers. Read more about the dos and don’ts of Viton chemicals.

The main problem with the Viton is its price. In production, it costs about 8 times as much to manufacture the same amount of material as EPDM. When purchasing a product that contains only a small amount of these rubber materials, the price may not vary significantly. But when ordering in large quantities, you can expect Viton parts to be significantly more expensive than EPDM.

Viton and EPDM seals
Viton vs EPDM Sealing Rubber Chart

So which material is the best? These questions are not entirely fair. Both materials have specific applications where they are great for, so it all depends on the job they’re going to be doing. Our CPVC Ball Check Valves and CPVC Swing Check Valves are available with Viton seals or EPDM seals. These seals are made of O-rings installed in the fittings. These valves are all designed to be easily disassembled for easy maintenance, so they have removable bodies.

If you need a valve for a water system, regardless of temperature, a valve with an EPDM seal is usually the best choice. Aside from slightly different temperature tolerances, the main difference between the two materials is their chemical resistance. Viton is great for use with fuel and other corrosive materials, but when dealing with something as innocuous as water, this extreme durability is unnecessary.