The Chemistry
EPDM is one of the most popular pond liner materials on the market due to its high flexibility, ease of installation, and high UV resistance. EPDM stands for Ethylene Propylene Diene Monomer. That’s an intimidating name that refers to a synthetic rubber with a particular molecular structure. For those chemistry enthusiasts, EPDM has a single bond, chemically saturated backbone, making it extremely resistant to outdoor conditions like UV exposure and ozone. This means it is resistant to the cracking and discoloration that comes with this kind of exposure. In other materials, cracking is a particular concern because it could lead to leaks that may be impossible to repair, since the surrounding material is typically compromised as well.
Unlike EPDM, rubbers with double bonds, as in natural rubbers, have a molecular structure that is more vulnerable to the effects of outdoor weathering unless it is treated with special protective coatings.
Getting back to the chemistry, EPDM is made from ethylene, propylene, and a diene comonomer that enables crosslinking. Crosslinking creates a more mechanically stable structure that enables excellent tensile and elastic properties. There are thousands of different formulations of EPDM materials that can be manufactured, starting from the choice of EPDM polymer, then the processing and curing methods used. BTL’s AquaProFlex EPDM pond liners are produced from a cured single-ply membrane which is formulated to be 100% fish and plant safe, durable, and extremely flexible.
Functional Pros and Cons
One major concern that pond owners often ponder (did you see what I did there?) is the longevity of the liner they purchase. It’s no fun to spend hours of sweat, tears, and money on building a pond that must be deconstructed and relined in just a few years. While the functional longevity of EPDM can vary according to the application and working conditions it’s subject to, high quality EPDM liners, properly installed and maintained, can last for 20 years or more, and many have been known to top 30.
Of course, no liner material is perfect, and EPDM does have some vulnerabilities, but most can be avoided or managed with reasonable planning. The primary vulnerability to EPDM is that it’s extremely vulnerable to solvents, hydrocarbon oils, and even some lubricants. Fortunately, these are rarely found in a garden pond or fishpond environment. A wise pond owner, however, will ensure that the installation crew (professionals or volunteers) don’t track any of these contaminants into the pond on their shoes. Beware of shoes that are worn in a workplace that works with these materials, and even those that have trekked through the garage on the way to the backyard. A few minutes of caution and some disposable shoe protectors can prevent a major disaster from striking your beautiful new showpiece.
This is probably not a big concern, considering that your pond is designed to be full of water, but it’s worth knowing that EPDM is not flame resistant. That’s actually a good thing, because the presence of fire-retardant treatments, like those employed for EPDM roofing material, can render the liner toxic to your fish. So, keep open flames away from your materials, especially during installation, and take a moment to appreciate the attention to detail we offer in our fish-safe EPDM liners.
A Proven Workhorse
EPDM, as a material, boasts many excellent physical properties, and it’s easy to understand why it is one of the most popular and enduring pond liner choices. In fact, it’s used for an enormous variety of applications, based on its formulation and structure. EPDM is widely used in roofing applications, but it can also be used as a sealant in expansion joints, weather stripping and garage door seals. It’s even used on RV roofs and as a waterproof coating for bitumen roofs. Seals on your refrigerator and freezer may be EPDM, where it also acts as an insulator. EPDM’s insulating properties and temperature tolerance makes it an excellent choice for use on face masks for industrial respirators, and its high tolerance for weather exposure and UV rays make it suitable for garden hoses.
All EPDMs are Not the Same
Of course, each of these EPDM applications may have formulations and properties that vary considerably from the carefully selected properties of our EPDM pond liner. We strictly advise against seeking out cheaper versions of EPDM sheet materials, like roofing membrane, to line your pond. Any material that’s not intended for this application and not certified as fish and plant safe presents significant risks to your pond. Roofing membrane is often treated with flame retardants and algaecides which can leach into your water and damage or kill your prize specimens. Worse, the effects may not appear for months down the line, and a gradual fish kill, or plant die off, may be attributed to some other cause. Simply changing your water and repopulating the pond won’t fix the problem and your new residents may soon suffer the ill effects of a toxic liner.
