Choosing a Fish Safe Liner Material when Building a Fishing Lake

Flexible liners solve a lot of the challenges of lining a large fishing lake, but they’re not all equally qualified for the task. While some polymers work great for drinking water supplies or holding oil field waste, they may not fit the needs of fish in a natural environment. Some materials may work just great for the fish, yet they can’t deal with the challenges of exposed outdoor installation and quickly break down. When shopping for flexible liners for fishing lakes, that will last a decade or more, start and end your search with reinforced polyethylene (RPE). Here are all the reasons why RPE beats out the competition when searching for the ideal fish safe liner material.

Leaching Out Chemicals

The biggest concern over polymer liner selection involves a group of chemicals known as plasticizers. These chemicals help the material stay flexible and resist tearing and cracking, especially when it’s cold or otherwise rigid. However, these same chemicals tend to leach into the water of the lake. They’re not all toxic to fish, but as a class of contaminants they negatively affect the growth rate of most fish. It may also be unsafe to consume fish that were exposed to these kinds of chemicals on a long-term basis. That’s why all commercial aquaculture businesses, that produce edible fish, must use food-safe liners and not just fish-safe liners. Even if you don’t plan to use a food-safe material in your pond, you’ll need a liner you can trust to not kill or stunt your fish. Polyethylene, in general, is free from chemicals that could be a problem, but RPE in particular has no need for additional plasticizers and is almost always fish-safe.

Reacting to Sunlight

Any polymer installed outdoors is at risk for breaking down from constant UV exposure. The sun’s rays don’t just damage human skin, they also destabilize the materials of polymer liners to leave some peeling and cracking after just a few years of use. PVC, in particular, is known for being weak against the sun’s constant weathering effects. Some polymer liners only begin to leach out fish-damaging chemicals if they’re exposed to UV rays. It’s possible to cover the liner with a thick layer of sand and soil to keep the light away from the material, but it only takes one patch of soil shifting out of the way to cause a problem. Start with an RPE material, that is highly UV resistant instead, to ensure you don’t have to worry if the liner becomes exposed at any point.

Being Buried

Speaking of burying the liner, it’s a common and recommended practice for fishing lakes because fish thrive in natural bottomed lakes. There’s no reason you can’t have both a liner and a natural bottom since you can add as much sand and soil as necessary over the liner. Yet if you plan to do this, you’ll need to choose a liner that won’t shift and tear as the weight of both the soil and water builds up from above. This is where the reinforcement in RPE comes in handy. The reinforcement grid greatly increases the tear and rip resistance of the material. Even when the weight of the soil presses the liner against a void or a sharp rock, the reinforced polyethylene will resist tearing under far greater weight than related materials like low density polyethylene (LDPE).

Shifting Soils

Another situation in which RPE’s reinforcement makes a big difference involves the shifting of soil. Proper excavation and compaction are the key to building a base of soil that can take the weight of the water. Each cubic foot of water weighs 62 pounds, so each square foot of liner can have hundreds of pounds pressing down on it and pinning it against the soil below. What happens if that soil slides out of place and leaves nothing but the weight pressing down from one side? If you’ve chosen a weaker liner material, a rip is almost guaranteed to occur. A reinforced material, like RPE, is much more likely to withstand the force and stretch if necessary rather than ripping and tearing.

Dam and Spillway Protection

Don’t forget that dams and spillways need to be lined just as much or more as the rest of the lake. Water rushing over bare soil during a flood or spill will only cause serious erosion that leaves gullies behind that aren’t so easy to fill in. A concrete lined spillway is a good idea, but the basin that holds the water until it can be pumped or released must be lined to prevent seepage and further spills. RPE will work just as well for protecting the spillway and dam from erosion as it does for the bottom of the lake.

Ease of Installation

Finally, consider the thickness and weight of the liner material and how that will affect the installation process in particular. Fishing lake projects tend to be completed with a combination of heavy equipment and hand labor, and that extends to the liner installation. Liner materials that are too thick and stiff will take a lot of extra labor to spread across the ground and fit into the corners. EPDM is a thick and heavy liner material that is not recommended for large projects like fishing lakes for this particular reason. Look into the seam sealing process as well. While it’s recommended you order a custom fabricated sheet that needs as little seaming as possible, it’s often impossible to completely avoid the need to seal a seam. Liners like RPE that can be sealed with both heat and solvents are versatile and easily adapted to the challenges of the specific installation.

As you can see, RPE outperforms all the other options like PVC, HDPE, LDPE, and EPDM. That’s why we offer it here at BTL Liners for our liner products, including those for challenging installations. Shop our selection of fish-safe liners to find the perfect product for a fishing lake of any size and design.


Liners by BTL

AquaArmor Pond Liner

The most versatile liner on the market today, AquaArmor maximizes protection from harmful UV rays, tear resistance and punctures that cause leaks. Simply the best liner on the market.

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