Pond Liner

Liner Sizes: 15' x 25' | 20' x 40' | 25' x 50' | All Pond Liner Sizes

Cheap pond liner is perfect for building a pond. It allows the pond owner to create ponds of various shapes and depths. Sometime, when it comes to small backyard ponds I often prefer to use the pre-molded ponds instead of using an EPDM Firestone 45 Mil Liner...I dunno...it just works great to use a ready-made pond in the small scale. I've installed many of those hard shell ponds and they are fairly easy to install except for maybe some issue with leveling things out after you've dug the pond hole. For large ponds over 8 x 10 there really isn't an option for a molded pond so a liner is the only way to go. Many complete pond kits on the market include a large piece of pond liner along with the skimmer and filter falls.

Sizes: 15' x 25' | 20' x 40' | 25' x 50' | All Pond Liner Sizes

When it comes to larger ponds I almost exclusively use the 45 mil fish-safe pond liner. After 2010 Firestone, one of the more familiar manufacturers, switched to a 40 mil thickness liner which is now the standard for landscapers and pond builders although 45 mil is still available. Unless you are using a molded plastic formed pond or are digging or excavating a large natural earth pond in blue clay then you will likely need to use a pond liner.

A pond liner is basically a resistant and watertight membrane that keeps the water in your pond. Pond liners can be the most expensive piece of the initial pond build so make sure you measure twice and order once because the planning of your pond is the key to success!

After you have done the initial layout of your pond and maybe even after you have sharpened your shovels and started digging the shape of your pond out of the front lawn you should stop and do some simple calculations to figure the size of the liner you will need. Establish the size of the liner before going to far in to your planning as the importance of correct sizing when using a membrane cannot be overstated. When a liner is costing over $1.50 per square foot you want to be very careful before you order the sheet of EPDM that is 380 square feet only to discover you needed a piece that is 780 square feet! I've been there and it's a long way back!!

So we'll assume that you will be requiring a pond liner which is also called a membrane. Smaller basins and backyard ponds only require a lightweight material. We use a PVC, polyvinyl chlorine, membrane that will resist frost and ultraviolet light. Sunlight will damage cheap materials so it is best to ensure your membrane has this protective feature, most do but you should ask your supplier. Most 20 mil membrane should cost around $1 per square foot and can be bought in standard sized rolls or get a custom size piece cut at your local garden supply store as most such retailers carry this and the 35 mil liner that is slightly thicker and can buy for $1.50 per foot. The 20 mil and 35 mil materials should come with a 20 year warranty if you place a geo-textile protective barrier under and on top of the liner.

There is a 45 mil EPDM, ethylene-propylene-diene-terpolymer, heavy -duty membrane that is available and we often use this strong and puncture resistant material for waterfalls and streams between two basins. It can cost from $0.80 - $1.50 per square foot. Using a thicker material will reduce the risk of a breech or puncture which could result in you're fixing a leaky pond. Luckily, these membranes can be repaired and sealing foam is available to help with sealing a pond.

Calculating pond liner size
Many beginners take measurements from their outline and do some rough calculations and then scurry off to the pond supply store with such enthusiasm only to come home with a specially-cut length of material to find that it is too small. Here is a simple formula to help calculate the dimensions of the pond liner you'll need.

Width - The formula to determine the width of your membrane is 2 x pond depth + pond width + 2 feet = required width.
Length - The formula to determine the length of your membrane is 2 x pond depth + pond length + 2 feet = required length. .

Example: If you have a 20 foot long x 10 foot wide pond that is 6 feet deep at the deepest point, the calculation would look like this:

20 (width) + 6 (depth) + 6 (depth) + 2 (overlap) = 34 feet in length minimum membrane liner width size required according to the pond liner calculator.

10 (length) + 6 (depth) + 6 (depth) + 2 (overlap) = 24 feet in width minimum membrane liner width size required according to the pond liner calculator.

In this example you would need a liner at least 34' x 24'...unless you have a custom cutting facility nearby you may need to buy a standard sized roll. Many manufacturers offer standard rolls of 45 MIL, 30 MIL and 20 MIL liner at low-cost.

Remember it can be much cheaper to modify your pond plans to accommodate a standard liner roll size. In the above example a 30 foot by 30 foot liner can be bought for 15% less than a 34 foot by 24 foot custom piece! Be flexible...that's what pond life is all about!

Don't forget to add whatever you will need to cover the waterfall spillway if your design calls for that. You can use scrap or leftover pieces for this, but just be sure you have enough left to do the job you've intended. As my Bass fishing buddy Jared said to me one day as we drifted into the shoreline reeds, pond liner is a bit like Budweiser...it's better to have a bit left at the end of the game instead of running out before the end of the fourth quarter!

We All Want The Cheapest Pond Liner
Sizes: 15' x 25' | 20' x 40' | 25' x 50' | All Pond Liner Sizes


When looking at pond liner there are various thickness and strengths which resist tearing and puncturing to a lesser or greater degree. A pond liner, if installed in sharp rocky terrain may need a geo-textile covering and a sand underlay in order to prevent any sharp edges from causing a hole that may leak in the future. The 45 MIL liner is the industry standard and there are a few brands and manufacturers and as long as the thickness is guaranteed to be the 45 MIL then the only difference you need to consider is price.

EPDM Liners like the omnipresent PondGard by Firestone® is ideal for most backyard ponds and can be found in many local garden supply stores, the Firestone® PondGard 45-mil EPDM liner is the liner of choice for many do-it-yourself type of pond builder as well as professional contractors who need reliability and a long -life product and this rubber compound fits the bill. Extremely flexible, it is easy to work with and will stretch to conform to a pond's features. It is completely UV-resistant and will hold up well in direct sunlight. Carries a Firestone® 20-year warranty.