Why Do You Need a Pond Liner?
Pond liners keep water from draining into the soil. They form an impermeable layer between the water and the soil, preventing water loss.
However, a pond liner only works if it’s free of leaks. In practice, a liner can develop leaks for three reasons:
1. Punctures or tears in the fabric.
2. Leaks in seams in the liner fabric.
3. Age and deterioration of the liner fabric.
Puncture and Tears
The risk here is that small rocks, tree roots or other objects may remain in the hole excavated for the pond. These may not be obvious, but once you install the liner and fill your pond, the weight of the water pressing down on the liner material may be enough to puncture it. To avoid that risk, you want a good, strong liner material.
Leaks at the Seams
Your pond liner will more than likely be made out of multiple sheets of liner material that are welded together. Leaks can occur any place where a seam joins two sheets. The key question is whether the welding is done in the factory or in the field during installation.
Factory-welded, custom pond liners are the best option to avoid seam leakage. Factory welding can use advanced technology that produces more consistent welds. The welding is also performed under controlled conditions. In contrast, welds made in the field during installation need to deal with uneven ground, weather, less sophisticated welding equipment and other factors that lead to less than perfect welds.
Another important question for fish ponds is whether your pond will have a dock. If so, the dock’s columns will penetrate your liner, creating another point where leaks can happen. In this case, you need to go with a custom liner with specially-made column boots for the dock.
UV and Weather
Your pond liner needs to age well to avoid leaks. That means that the liner material must be resistance to UV rays and to weather. Liners are made out of synthetic materials characterized by long chain molecules. UV rays can break these long chain molecules over time, causing the material to become brittle and crack.
To avoid this, chose a liner made from a material that is either inherently resistant to UV, or one that has a protective coating.
Choosing the Right Liner Material
Choosing the right pond liner can be tricky, since the best choice depends on your specific needs and environment.
Ideally, your vendor should offer liners in a variety of materials. If you ask a vendor who sells only EPDM liners, don’t be surprised if they tell you that EPDM is a great choice for any pond, no matter what.
For a fish pond liner, the most important characteristics are:
• Flexibility (to better fit the contours of your pond)
• Strength and resistance to stretching
• Puncture resistance
• Weight (for easy handling)
• UV resistance
• Long lifespan
We manufacture liners using over a dozen different materials. In our 30 years’ experience, we’ve found that two liner materials best fit the criteria for fish ponds: Reinforced Polypropylene (RPP) or Reinforced Polyethylene (RPE).
RPP is best for smaller ponds. It’s one of the longest-lasting liner materials available and has a coating that is highly resistant to UV and weathering.
RPE is best for larger fish ponds. It’s an excellent, affordable material that is highly resistant to punctures and has the maximum resistance to UV rays.
Regardless of the material you choose, make sure you know the manufacturer’s warranty for the liner.
How Much Liner Do You Need?
These calculators work well if you have a pond that’s generally round or oval in shape. If you have an irregularly-shaped pond, say with a bend or a kidney shape, ask our staff prepare a better estimate of the size you need.
Note that your pond liner will need to be slightly larger than your pond. You need 5 feet extra around the rim of the pond to allow the liner to be secured in a trench. Make sure that the calculator you use considers this.
How Complicated is Pond Liner Installation?
If your liner is manufactured in a single piece, you can install it yourself, so long as you follow proper procedures. We’ve written a complete guide to installing pond liners that you can review.
Installing a pond liner made of multiple pieces requires a welder with experience installing pond liners.
Before ordering your liner, make sure that the manufacturer will wrap it in a protective layer of felt. You don’t want it getting damaged during shipping.
Once the liner arrives, be sure to thoroughly inspect it before you sign for the delivery.
Unroll the liner in your pond, and then secure it. To secure the liner, you will dig a narrow trench around your pond, tuck the edges of the liner in the trench and then fill it to hold the liner in place. The size of your trench needed depends on the size and slope of your pond. Read our installation guide for more on this and other tips.
Still have questions? Not sure which liner material is best? We’re happy to answer your questions.