What Does EPDM Stand For?

EPDM, short for Ethylene Propylene Diene Monomer, is a highly durable synthetic rubber known for its excellent weatherproofing and resistance to sunlight, temperature fluctuations, and many chemicals. Commonly used for roofing, automotive seals, and small pond liners, EPDM has carved out a niche in applications that require flexibility and resilience in the face of the elements. 

However, despite these strong qualities, EPDM has some limitations which can make it unsuitable for certain uses. In particular, it isn’t suitable for use as a liner for large ponds or containment pits because of its lack of strength and tear resistance.

What is EPDM Made Of?

EPDM is a synthetic rubber derived from ethylene, propylene, and a third compound, diene, which provides flexibility. The material is polymerized into rubber sheets or forms that can be rolled, molded, or otherwise fabricated to suit various industrial needs. Ethylene and propylene, key building blocks, give EPDM its resistance to heat and UV radiation, while the diene component creates a structure that enhances flexibility. EPDM also typically contains additives like carbon black, which helps improve weathering resistance, and stabilizers to prolong the material’s lifespan in outdoor conditions.

The structure and material composition of EPDM give it its unique properties, making it resistant to ozone, UV rays, extreme temperatures, and certain chemicals.

What Are the Advantages of EPDM?

EPDM has a range of properties that make it advantageous for specific applications, especially those exposed to weather elements:

• Excellent Weather Resistance: One of the primary reasons EPDM is used outdoors is its ability to withstand harsh weather conditions. It can endure long-term exposure to sunlight without degrading, as it resists UV rays and ozone.
• Temperature Resilience: EPDM can perform well in extreme temperatures, from as low as -40°F to as high as 300°F (-40°C to 150°C). This makes it highly suitable for both cold and hot environments, as it can handle temperature swings without cracking or losing elasticity.
• Chemical Resistance: The material is resistant to a variety of chemicals, including certain acids, alkalis, and even some polar solvents. This is especially useful in applications where chemical exposure might be an issue, such as industrial settings.
• Flexibility and Elasticity: EPDM retains its flexibility, even in colder temperatures, making it ideal for applications where material flexibility is necessary. For example, EPDM is frequently used for roofing and automotive weather seals, where the material must adapt to shifting temperatures without becoming brittle.

These attributes make EPDM a top choice in a variety of industries, from construction to automotive to landscaping.

What Are the Disadvantages of EPDM?

Despite its weatherproof and resilient qualities, EPDM has a few significant drawbacks that can limit its application in certain scenarios.

• Not Suited for Large Ponds: EPDM comes in 50-foot wide rolls or smaller, which means that for larger pond installations, installers will need to glue or tape multiple sheets together to cover the pond bottom. This makes installation more expensive due to the additional labor and materials needed.  It also increases the risk of a leak at the seams over the life of the pond.  Other materials used for pond liners can be welded together, which reduces the risk of leaks.
• Lack of Tear Resistance: One of EPDM’s major weaknesses is its lower resistance to tearing compared to materials like PVC, polyurethane or reinforced polyethylene . This makes it unsuitable for high-stress environments where durability is critical. For example, while it can work for small ponds, it is not recommended for larger water bodies where constant exposure to moving water, shifting ground or external forces could cause tears.
• Weak Tensile Strength: EPDM is not as strong as some other rubbers or plastics, meaning it doesn’t perform well under tension. In applications that require stretch or the handling of heavy loads, EPDM is prone to deformation, which can compromise its performance and lifespan.
• Vulnerability to Oil and Hydrocarbons: Although EPDM is chemically resistant to a wide range of substances, it does not fare well with oil-based products and hydrocarbons. This can limit its use in industries where oil and grease are common, as the rubber can swell and deteriorate with prolonged exposure.
• High Weight: Weight becomes increasingly important the larger the project. The material has to be shipped, unloaded and handled into place, and covering a large area with the lightest and most flexible choice of material makes economic and engineering sense. EPDM is heavy and rigid, making shipping and handling expensive.
• High Installation Cost: While EPDM itself is relatively affordable, installing it can be labor-intensive. In roofing, for instance, EPDM installation often requires adhesives or even specialized tools, which can drive up costs compared to other materials.

These weaknesses make EPDM less versatile for applications requiring strength and high durability.

What Applications Are Good for EPDM?

Given its weather resistance, flexibility, and durability against UV rays, EPDM is best suited for outdoor applications where strength is not the top priority.

• Roofing: EPDM is popular in commercial roofing because it’s resistant to extreme temperatures and UV radiation. Flat and low-slope roofs benefit from EPDM sheets, which provide a durable seal against water and harsh weather.
• Automotive Seals and Hoses: In the automotive industry, EPDM is often used for window and door seals, weather-stripping, and hoses. Its resilience in various temperatures and environments helps keep cars protected from water and debris while providing an airtight seal.
• Small Backyard Ponds: EPDM is a common choice for small pond liners due to its flexibility and weather resistance. If you buy a pond liner at a retail store such as Home Depot, it is likely made of EPDM. However, it is best suited for very small ponds where there isn’t significant pressure or movement of water that might lead to tearing.
• HVAC Systems: EPDM is commonly used in HVAC systems to seal joints and prevent air leakage. Its resilience to both heat and cold is beneficial in this application, as it can function well across a wide range of temperatures without cracking.

Limitations of EPDM for Large Ponds and Chemical Pit Liners

In larger pond applications, EPDM’s tendency to tear and lack of tensile strength make it less ideal. For example, in commercial ponds or reservoirs where ground movement, water pressure, and potential abrasions from debris are frequent, EPDM may require regular maintenance or replacement.

For chemical pits containing oil-based materials or chemicals with high volatility, EPDM’s inability to resist hydrocarbon exposure makes it unsuitable. Additionally, for large pits where a single, seamless installation is preferable, EPDM’s adhesive-seam method may be insufficient for maintaining structural integrity.

RPE: A Better Alternative for Large Ponds and Chemical Pits

Reinforced Polyethylene (RPE) is a durable, flexible material that surpasses EPDM in strength and tear resistance. Here’s why RPE is often recommended for larger pond and chemical pit liners:

• High Tear and Puncture Resistance: RPE offers far greater tear and puncture resistance, making it suitable for high-stress environments.
• Heat-Welded Seams: RPE sheets are commonly joined using heat welding, which creates a stronger, more durable seam than the adhesive seams used in EPDM. This is crucial for maintaining the integrity of large installations.
• Lightweight and Cost-Effective: Despite its strength, RPE is lighter than EPDM, simplifying transport and installation. For larger installations, RPE can also be significantly more affordable.

Western Environmental Liner offers high-quality RPE products tailored for commercial pond liners, providing custom sizes up to 150,000 square feet. Their RPE liners are ideal for large ponds, waste containment, and even chemical pit liners where high durability and resistance are key. The Aqua Series 30-mil RPE, for example, has the strength to withstand challenging conditions at a lower cost compared to EPDM​.

Back to All Articles