Large commercial ponds require some kind of flexible or poured-in-place liner since they’re simply too large to cover with a pre-cast cover. However, many homeowners are familiar with the stiff pre-shaped pond liners sold by home improvement stores and water garden suppliers. These preformed liners are popular, but they’re not the best option for even most homeowners adding a small pond to their backyard. From koi ponds to fountains, flexible pond liners are generally a better choice for hobby ponds than stiff pond liners. Compare the two options before making a purchase or choosing a design.
Limitations on Size and Design
When shopping for preformed liners, you’re limited to whatever designs you can find. If you want a unique looking small pond, you’ll need to stick with flexible liners. Preformed liners also tend to be limited to just a few hundred gallons at the most. In order to raise koi and water plants, you’ll usually need at least 500 to 1,000 gallons to provide a healthy environment. Fish can require anywhere from 10 to 150 gallons of water per inch of fish, so the total volume quickly adds up. Most preformed pond liners are too small to use for much more than decoration.
Ordering a small amount of flexible liner is more affordable than you might assume. You can buy a professional grade multi-layered RPE (reinforced polyethylene) liner product without spending more than a few hundred dollars when covering a backyard pond. Most preformed liners start in the hundreds and can reach up to thousands of dollars despite their other drawbacks. Don’t assume that an inexpensive preformed liner will save you money either. With a shorter lifespan and greater chance of damage from routine cleaning, preformed liners tend to cost more over time. Factor out the cost of ownership and not just the upfront installation costs when comparing preformed and flexible liners.
Damage from Freezing
If you’re located in a cool or cold climate with freezing winters, you’ll want to stick with flexible liners over preformed ones. The flexible material moves with the soil or water as it expands, while preformed liners are more likely to crack or rise up out of place. Frost heave occurs when wet soil underneath the pond expands as it freezes. This causes upward pressure on the bottom and sides of the pond, which isn’t a problem for flexible materials. If a pond is small enough to freeze solid in a cold climate, the ice expansion will push outward on the liner. Again, it’s not a problem for most flexible materials. PVC liners can become brittle in winter temperatures, but multi-layered RPE liners stay flexible and expand as necessary to prevent frost damage.
Leveling and Smoothing
Preformed liners also require you to spend far more time on leveling and smoothing the ground for proper support. Since they’re shaped in molds at a factory, there’s a small margin of error on shaping the soil so there’s no voids left under the liner. Ponds can shift and leak if the preformed liner isn’t installed in a properly shaped space. Flexible liners conform to the space you create, reducing the work necessary for installation and providing a more natural look.
No matter how small your backyard pond, a flexible liner is always a better choice than a preformed one. This is especially true if you want to raise koi, other fish, or water plants. Order a flexible geomembrane material from an experience supplier like BTL Liners for easy installation and better long-term performance.