Even once you’ve narrowed down your liner choices to a flexible material, you’re still left with plenty of options. With most liner materials sharing the same black color and relatively similar thickness and flexibility, telling them apart by sight alone is often difficult. Yet liners that look identical to the eye won’t provide the same performance in the same conditions. Checking the specific material composition of each pond liner you’re considering tells you more about the product’s performance than any marketing claims. Understanding the strengths and weaknesses of each flexible pond liner material is the key to choosing the right one for your particular purpose.
PVC
Polyvinyl chloride (PVC) is one of the most commonly used plastic materials in the world. Not only is it used for making pond liners, it’s also popular for plumbing due to its relatively safety for potable water use. While it’s a widely used pond liner, found in both small and commercial scale ponds, it’s far from the best flexible liner for most installations. This material is heavier than reinforced polyethylene (RPE) products, resulting in slower installation that is more labor intensive. It’s also less puncture resistant than RPE. This increases the likelihood you’ll need to patch a few rips and holes from rocky ground before filling the pond with water. PVC is very susceptible to damage from UV rays when installed in an exposed way and most liners made from it feature plasticizing chemicals that aren’t safe for fish. It’s also the material most likely to crack in cold climates due to becoming brittle when cold or frozen.
EPDM
Flexible sheets of Ethylene Propylene Diene Monomer (EPDM) were once the primary option for lining a pond, regardless of its size or purpose. This material is often referred to as rubber liner because it’s thick, slightly squishy, and highly flexible. Yet to offer the same durability and tear resistance, an EPDM liner must be much thicker and heavier than a LDPE or HDPE liner. This makes a big difference during installation since the heavy EPDM takes a lot of time to unfold and spread across an acre or more of ground. EPDM is also heat-resistant and therefore seams must be sealed with seam tape, which is a slower and less reliable process. It does offer the highest amount of puncture resistance and flexibility for tight corners, but the material is otherwise a costly and heavy way to line a large pond.
Polypropylene
For exposed liner installations, reinforced polypropylene (RPP) materials are often the only choice. This liner offers the greatest amount of UV resistance of all your options. If you’re making a demanding evaporation pond that will experience high levels of chemical exposure or abrasive wearing, RPP will likely need an underlayment of RPE material. If you choose a multi-layered RPE liner instead, you can still enjoy surprising longevity with exposed installation while reducing the need for underlayment. RPP liners are also more expensive and harder to find than polyethylene based products, especially for smaller backyard projects rather than large scale installations.
LDPE
Low density polyethylene (LDPE) is often mistaken for high density polyethylene (HDPE) since they’re both made from the same basic type of plastic. However, the density of the polyethylene makes a big difference when used for pond lining. LDPE is slightly more flexible than HDPE and comes closer to the flex offered by EPDM materials. You’ll commonly find LDPE products used for liners and covers over greenhouses or ponds rather than as the liners under the water.
RPE
With an optimal combination of high durability, light weight, great chemical resistance, and good UV resistance, multi-layered RPE is the best all-around material for a pond liner. Whether you need a fish safe liner, want something that can handle coal ash and natural gas saline, or just need an affordable product for your backyard, multi-layered RPE meets all of your needs. It’s still flexible enough to conform to any custom design with shelves and overhangs. It’s also highly impermeable for minimal water loss thanks to the woven-coated manufacturing method. Multi-layered RPE is particularly tear and rip proof, making it ideal for installing over rough soil that would damage other materials. Finally, multi-layered RPE offers the most options for custom fabrication. The material can be produced in large dimension rolls to minimize seams and is easily heat welded at the factory for custom one-piece fabrications. If you prefer to use rolls and assemble on-site, you can choose from heat welding equipment, seam tape, or adhesives to finish the job.
You’ll find that most recent landfill installation or capping products rely on multi-layered RPE liners and covers because of its durability and strength. In dry conditions like landfills, the material has lasted over 30 years without degradation or damage. Despite being highly durable and chemical resistant, it can also be affordable.
Other Materials
You may also find box-welded pond liners listed as a separate option for flexible lining. These products tend to be made with some kind of polyethylene or a PVC material. They’re cut and welded into shape at a factory and tend to come with some of the same limitations as preformed plastic pond liners. You still need a lot of extra excavation work to get a perfect fit for the liner and they’re limited in size to a few thousand gallons. However, they are still somewhat flexible due to the use of liner material. Unless you’re making a small decorative pond and need a box-welded liner for some reason, you’re better off sticking with rolls of material instead.
Reinforced vs Non-Reinforced Pond Liners
You’ll notice that in the sections on polypropylene and multi-layered RPE the term reinforced was used to describe some liners. A reinforced geomembrane is one made with reinforcing scrim tape between outer coating layers. This core creates a ripstop function that prevents small tears and holes from growing thanks to the interlocking strips of tape. Reinforced pond liners are much more durable and highly recommended regardless of use. If you plan to clean your pond out at any point in the future, having a reinforced liner installed from the beginning will minimize chances of tears or damage leading to leaks. The multi-layered construction helps the material flex instead of tearing, reducing strain from freeze and thaw cycles as well.
With a clear view of the benefits and disadvantages of each of these common pond liner materials, you should have a better idea of what’s right for your project. A multi-layered RPE is likely to work for most projects, whether they’re residential or commercial. If you’re wondering which liner material to choose for your pond, reach out to us here at BTL Liners for more help.
