Choosing a Pond Liner
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A good strong liner is the base of any successful pond. Without a liner, your pond will likely lose all its water quite quickly. There are quite a few different material and brand choices out there, which can be a little confusing at first. In this section, we will simplify the choice into one of two liners based on your particular needs. Here are a few requirements that we recommend when choosing a liner:
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Strong and puncture-resistant
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Easy to work with and install
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Fish and plant safe—doesn’t contain harmful chemicals that will leach into the water
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Is available in a single piece large enough to fit your entire pond without having to
join two liners together
A vital thing to keep in mind when choosing a liner is number 3 above—make sure it’s fish and plant safe. Some liners out there contain harmful plasticizers that can be poisonous to fish and plants. Rest assured that any liner we recommend and sell is 100% guaranteed not to leach harmful chemicals into the water. Some of our liners are even NSF certified for human drinking water applications.
Have liner questions? Visit our FAQ page
In our opinion, there are two main choices for liners when building a natural-style ecosystem- based pond or water garden. These are EPDM rubber and reinforced polyethylene (RPE). Both have advantages and disadvantages, depending on your particular project. If you’re building a formal-style water garden, you also have a third option: custom box-welded liners. Box-welded liners come custom heat welded into ready-to-go 3D shaped boxes, L shapes and cylinders, with no folding or pleating necessary.
3D Shaped Box-Welded Liners: Rectangular Box-Welded Liner Inserts
EPDM rubber liners have been the standard liner material for decorative ponds for a number of years. The main advantage of EPDM is that it’s very flexible and malleable. This makes it a good choice for ponds with a lot of bends, shelves, corners and curves that require folding and pleating the liner to get a good fit. The downside of EPDM is that it’s less puncture resistant and much heavier than RPE. The weight of a liner is less of an issue in smaller pieces, but for medium or larger ponds or small lakes, EPDM quickly becomes unmanageable because of weight.
RPE Liners (Reinforced Polyethylene)
Apart from being slightly less bendable and flexible than EPDM, reinforced polyethylene liners are stronger (2x to 3x more puncture resistant), lighter (about 1/3 the weight of EPDM), and can be made in very large single-sized pieces. In fact, we have delivered liners up to 60,000 square feet in a single piece—something that would not be possible with EPDM rubber due to the weight of the liner.
RPE is our go-to liner for most pond projects. In fact, for larger applications, we don’t even consider EPDM an option anymore. When we get into medium- and small-sized ponds, we still like RPE because of its higher strength. Because it’s a little less flexible than EPDM, it may take a little more effort to pleat and fold the liner into place. In our opinion, however, the loss of a little flexibility is worth the reassurance that we have a stronger liner in place. We will go with EPDM if a pond is very small, or if there are an exceptional amount of bends, shelves and corners in the pond that would lend itself to the extra flexibility of EMDM rubber.
Because EPDM rubber has a lower puncture resistance, it’s mandatory to use some kind of underlayment material under the liner to protect against anything rough in the soil. Traditionally people have tried to use all kinds of things as underlayment: sand, newspaper, carpet, etc. However, since geotextile underlayment prices are quite reasonable these days, it’s worth the extra cost to get a quality geotextile fabric that’s not going to rot like newspaper, smell like carpet, or sift away over time like sand. Underlayment should also be used underneath any larger rocks in the pond that could cause some abrasion to the liner during the process of placing a rock.
Underlayment for RPE
Because RPE liners are 2 to 3 times more puncture resistant than EPDM, as long as there’s nothing sharp in the soil, you don’t need to use an underlayment. Of course, if there are any sharp rocks, sticks or roots present, you’ll still want to use a geotextile-based underlayment to protect against punctures.
How big of liner do you need?
If it makes sense for your project, you should try to get one piece of liner large enough to fit your entire pond and waterfall. As we mentioned above, we can make RPE liners in very large sizes. In fact, we have delivered liners up to 60,000 square feet in a single piece. Seaming a liner on the project site is a pain and should be avoided unless you have some experience with seaming liners together. If a customer is ordering an RPE liner, we heat weld the liners together into any size in our controlled fabrication facility before shipping. Need an L shape or a T shape? No problem, we can make that. This is actually one of the advantages of RPE liners—we can heat weld them into any rectangular-based shape. The EPDM rubber liners are available in rectangular pieces only.
To figure out how much liner you’re going to need, the first step is to determine the dimensions and depth of your pond design. Once you know the dimensions, you can use our liner size wizard to calculate the size of liner needed.
Liner Size Wizard
To keep things simple, we’ve created a wizard that quickly and easily calculates the amount of liner needed for a pond. Visit the following link, and select the first pond style, “Vertical Walls.” Then type in the length and width of the pond and click “Calculate” to see the recommended size of liner.
Liner Size Wizard: https://www.everything-ponds.com/liner-size-wizard.html
Manually Calculating Liner Size (Optional)
The formula for Length:
- 2’ extra liner at edge + depth to bring liner down + total length + depth to bring liner back up + 2’ extra at edge
This simplifies down to:
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Liner Length = 4’ + length + depth + depth
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Liner Width = 4’ + width + depth + depth
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Here’s an example: if your pond is 12’ long by 8’ wide and 3’ deep you will need
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Length = 4’+ 12’+ 3’+ 3’= 22’
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Width = 4’+ 8’+ 3’+ 3’= 18’
Adding Liner for the Waterfall
If your waterfall is on the smaller side, or sits quite close to the edge of your pond, it is usually easiest to simply extend the liner size out a bit to cover the waterfall as well as the pond. When figuring out how much liner to add for the waterfall, add the vertical height of the waterfall and the horizontal distance from the lip of the waterfall filter to the edge of the pond. If the waterfall is 2’ high and the front of the waterfall filter sits 2’ back from the edge, then you’d want to get at least 4’ of extra liner. If the waterfall is placed in such a position that it’s awkward to just add length to the actual pond liner, you can also use a separate piece of liner, which we’ll discuss next.
Using a Separate Piece of Liner for a Waterfall or Stream
If you have a larger waterfall or a stream, depending on its placement, it can sometimes be easier to get a separate piece of liner instead of extending out the main pond liner. For example, if the waterfall or stream was on the corner of the pond, getting one large piece would mean extending both the length and the width of the main liner to cover the waterfall on the corner. This can result in having a lot of wasted material, which can increase the cost unnecessarily. For situations like this, you can buy a second piece of liner just for the waterfall. However, there are a couple important things you’ll want to do to prevent any leaks:
1) When installing the stream or waterfall liner, overlap it over top of the main pond liner so that it runs down over the edge of the pond at least a few inches. Installed this way, any water running down the waterfall or stream will run right into the pond without encountering a seam in the liner. Try to buy a little extra liner so you don’t come up short. You can always trim it to the perfect length after it’s installed.
2) Make sure there’s a constant slope downwards towards the pond from all locations in the stream or waterfall. This will ensure that the water will always be running downwards and won’t trickle back up the stream to create a leak.
Have liner questions? Visit our FAQ page