Selecting a pond liner will be one of the most important decisions you’ll make regarding the construction of your pond, but choosing one requires much more than looking for the lowest price you can find. After all, different products vary in their durability, resistance to sunlight and weather, ease of installation, and more. The first question to ask, therefore, is whether you want to design your pond around the capabilities of the liner, or to purchase a liner that conforms to your ideal pond.
It’s critical to take time with this decision early in the conception and design process. Consider your needs and research your options thoroughly before making your choice and beginning construction. After all, the costs involved in draining and relining a failed pond are often so high that many owners simply decide to abandon the project altogether.
There’s no single best product for lining a fishpond, so be wary of any information site that claims their product is always the best choice. While EPDM is a perennial favorite for backyard ponds and decorative installations, there are some circumstances where other products and materials will perform just as well or even better. So, as you’re beginning your search for a liner, consider the specific requirements of the project you’re planning and compare those to the characteristics of each material. When the qualities of a liner are well-matched to the specific demands of a job, success is an easy target.
Important Characteristics to Look For
Aside from pricing, there are some basic requirements for pond liners that should always be weighed when comparing products:
- Impermeability - this refers primarily to the characteristics of the material itself but should also take into consideration how the liner is laid out in your pond and what kind of seams are used for joining separate pieces.
- Strength and durability - a pond liner needs to be durable to withstand stresses like the inevitable scuffs and abrasions that occur during maintenance or with wildlife visits. Even mild scuffs can weaken the material over time and lead to tiny leaks that are hard to pinpoint. Damage from tears and punctures are easier to locate but can occur both during installation and over time. A small protruding rock that doesn’t seem like a big issue can become exactly that when there’s a constant force of water pushing against it, perhaps for years.
- Resistance to weathering, UV rays, and ozone. No matter how you anchor your liner along the edges, some parts of it are likely to be exposed to the air from time to time. If the water level often varies, by as little as an inch, that inch of liner will be subject to weathering, ozone, and UV radiation from the sun. UV rays can even penetrate the surface of the water, albeit weakly, but for liners that can’t withstand UV exposure, that can lead to significant degradation over the life of the pond. A degraded liner is more vulnerable to tears, punctures, and cracking, all of which can cause leaks. Worse, when such damage is caused by weather exposure, it often cannot be repaired because the surrounding material is equally compromised and cannot support a patch.
- Ease of Installation is an important consideration, whether you’re enlisting the help of a few buddies or paying professional installers. Some liner materials are extremely light and easy to fold, but they’re relatively weak and easy to damage during installation. It’s never fun to start a pond off with leaks. Other liners are extremely heavy and may require large machinery to move rolls about, if the pond you’re working on is large. Even for small ponds, heavy liners are unwieldy to work with, so you may need to recruit a few extra buddies for the afternoon.
If you’re working with a material that’s vulnerable to UV rays, you’ll want to make sure the installation is fairly simple, because you can’t cover the liner or fill the pond until all the seams, folds, and anchoring is complete. Plan on completing your liner install in a single day, if at all possible, and get that material protected quickly!
- Safety of fish and plants is an obvious concern, whether you’re raising prizewinning koi or experimenting with your first water garden. The trouble with choosing a liner based on word-of-mouth from online forums is that they’re speaking from personal experience, and some problems may not show up for a few years, especially for long-lived koi. Using a PVC liner that contains plasticizers to keep it flexible means that over time, your water may become contaminated with phthalates as the plasticizer leaches from the material. If you notice your plants or fish showing ill effects and even dying (or your prize koi failing to breed), not many pond keepers will relate the cause to a cheap, five-year-old liner. When you’re making your final choice, always be sure to verify that you’re choosing one that’s verified as fish and plant safe. To be extra confident, choose a liner which has been certified safe for storing drinking water - officially indicated by the designator NSF/ANSI 61.
EPDM Liners
EPDM has long been the traditional product used for small and medium decorative ponds. Since it’s been popular for many years, both the manufacturer and global fish-pond communities have decades of experience working with the liner in a myriad of conditions. That lends confidence to many new pond enthusiasts, and for good reason. EPDM is very flexible and bendable, which makes it a particularly good fit for natural looking pond installations. Ponds with an irregular outline, and those designed with submerged plant shelves need a flexible liner that can conform to these contours without too much difficulty.
However, the very characteristics that make it an ideal choice for conforming to a complex shape do offer some drawbacks. Specifically, because of how soft and malleable EPDM is, it’s somewhat easier to puncture and tear compared to a few of its competitors. To survive the rigors of installation, most EPDM used for ponds are relatively thick, making them heavy and sometimes unwieldy during installation. EPDM also absolutely requires the use of an underlayment to protect the synthetic rubber from rocks, sticks, dinosaur bones, or other mysteries hiding beneath your soil.
AquaProFlex EPDM liners by BTL are formulated for use in all types of water gardens, including garden ponds, koi ponds, formal ponds, and lakes. AquaProFlex is a top of the line synthetic rubber (EPDM) liner that’s 100% fish and plant safe.
- EPDM is an impermeable membrane and is used in many industries for waterproofing.
- EPDM’s strength & durability is above average in the pond liner market. It’s very flexible and can stretch, when necessary, without tearing or permanently deforming. Relatively thick sheets help the material resist punctures, but the use of an underlayment to protect the EPDM from damage from lifting rocks and runaway roots is required.
- EPDM offers excellent resistance to weathering, thanks to the molecular structure of the material. It’s highly resistant to both UV rays from the sun and the damaging effects of ozone. EPDM pond liners stay flexible in temperatures from -40 Fahrenheit to 175 Fahrenheit virtually eliminating the risk of cold cracking.
- EPDM is known for its ease of installation, which requires much less technical knowledge and skill compared to other high-performing liners. It’s always best to line your pond with a single panel of material, and EPDM is available in a wide range of sizes, as much as 50’ wide and 200’ long. Even If your pond is more than 50’ wide, it’s a fairly simple process to cut an additional panel and attach it using adhesive and seaming tape. You’ll clean and lightly rough up the surface of the EPDM to encourage a good bond, then use a roller to make sure the adhesive has thoroughly connected the two pieces. After that, you’re ready to go. It’s not much more complicated than patching a bicycle tire, in fact.
- EPDM pond liner is certified as fish and plant safe, meaning that no harmful toxins can leach out of the material into the water, even over years of use. Keep in mind, though, that this non-toxic guarantee doesn’t apply to all EPDM products, even sheet materials that look the same. Roofing membrane is commonly treated with chemicals to discourage the growth of algae and to make it fire resistant, for example, and the manufacturer makes no guarantee that other toxic materials aren’t used in the curing process. Don’t rely on a salesman’s assurance that another material is just as good as EPDM pond liner - stick with one that certifies on the packaging that it’s fish and plant safe.
