Pond Liners

Pond Liner Selection and Installation

Possibly the most important choice you will make in a building a pond is selecting the type of pond liner. Once this choice is installed there is no going back. There are two basic forms of pond liners:


Preformed Ponds

preformed 150x150 Pond Liners

Preformed Pond

Preformed Ponds are usually made of fiberglass or plastic. They are available in a range of sizes and shapes and are very durable. One of it’s advantages is that it is relatively easy to install. You dig a hole that conforms to the shape and size of the preformed pond liner  and set it in the ground.  Preformed liners will also work as above ground or partially above ground ponds. Fiberglass is also one of the most durable types of pond liner material you can buy. Some of the disadvantages of preformed liners are that they are more difficult to conceal and look less natural than the alternative flexible liners. It is more expensive on a square foot basis and the pond must be designed around the liner rather than the other way around. Most standard preformed ponds that I have seen are too small and not deep enough to accommodate koi but will work for goldfish. You can also build a pond out of concrete, but that is similar to building a pool and as such may require professional installation.


Flexible Rubber Pond Liners

butyl liner 150x150 Pond Liners

Rubber Pond Liner


Flexible pond liners are generally made of rubber or PVC. Rubber pond liners are heavier and more expensive but are less prone to punctures and  last longer than PVC linersRubber pond liners are usually made of butyl or more recently EDPM.  I have found rubber liners to be durable, flexible, moderately expensive and easy to work with. They come with a warranty and are expected to last over 30 years. Since I have used rubber pond liners in all my ponds, the remaining steps to for koi pond construction assume the use of a flexible rubber pond liner.


Pond Liner Size Calculator

The size required when buying flexible pond liner is calculated as follows:

  • Length- The length of the pond + 2 times the Depth plus 2 feet. The two feet are added to allow a 1 ft overlap around the edge of the pond.
  • Width- The width of the pond + 2 times the Depth plus 2 ft.
  • So for a 15 ft by 10 ft pond that is 3 ft deep the liner should be 23 feet long and 18 feet wide or 414 sq. feet in total.

A pond liner size calculator is below:


“Best” prices for PVC liner generally range from 35 cents to 40 cents per square foot. This liner is best suited for smaller ponds. EDPM rubber pond liner generally comes in thickness’ from 45  ml to 60 ml.  Both sizes are long lasting and come with warranties of 20 -30 years.  The current (June 2011)  “best” prices I have found online are typically 58 cents per square foot for the 45 ml and 74 cents per square foot for the 60 ml. These unit prices may vary depending upon the size of the pond liner and guarantees provided by the store. For most residential applications the lower cost 45 ml liner is more than adequate.

To compare prices for different types and sizes, click on Pond Liners


1) After selecting the pond liner, the next step is lining the hole with sand or material underlayments or both to cushion and protect the liner. The cost of underlayments depends on the type of material used but is usually between 15 cents to 20 cents per square foot.


2) Stretch the pond liner over the hole with rocks or some weight holding down the edges. Start adding water and the liner will stretch and start sinking into the hole. Periodically adjust the weights holding the liner as it fills. When the pond is full, trim off any access liner and secure the edges with whatever material you have selected. I generally use natural rocks for this purpose but for more formal designs slate or brick can be used as edging. If the pond bottom is close to the water table or sits on top of a spring or underground stream a relief valve needs to be added so during periods of high water it does not push up and displace the liner.

Fish Nov 10 4 small2 150x150 Pond Liners

Rubber Liner Covered by River Rock

3) I always add small rocks to cover the entire bottom of the pond. I generally use river rocks but just about any small smooth stone will do. Just stay away from any sharp edge rocks which could puncture the liner or limestone, that will raise the PH of the water causing a chemical in balance that is harmful to the fish. The number one reason for adding rocks is to enhance pond filtration. The rocks provide a huge amount of surface area for the bacteria to colonize on as they do in an indoor aquarium. This bacterial breaks down the fish waste and other organic debris that fall to the bottom. The second reason is that the rocks help hold the liner in place. Finally ponds with rocks and gravel on the bottom are much more natural looking than black pond liners covered with algae and the rocks also provide material in which to anchor water submerged plants in place. Most books I have read recommend periodic vacuuming of the ponds bottom. With a rock bottom I have never had to do that task and the water and bottom of my ponds have remained sparkling clear.

4) River rock should be at least 1 inch deep across the entire bottom of the pond and roughly costs about $50 per ton. At a 1 inch depth a ton of river rock will cover 200 square feet so the cost per square foot is about 25 cents.

5) So for rough budgeting purposes you can figure that the total cost for lining a pond is about $1.00 per square foot.

  • 60 cents per square foot for 45 ml EDPM liner
  • 15 cents per square foot for underlayment
  • 25 cents per square foot for river rock

You also will have the cost for excavation–labor, equipment and disposal of dirt– which of course varies based on how much you do yourself.

6) The sides of the pond are built up by stacking larger stones from the bottom to just above the water line. This contributes to the natural look but more importantly provides hiding places for small fish and fry. My fish have successfully reproduced every year without having to use breeding tanks or spawning mats to separate the fry from the adult fish. I have experienced the excitement of seeing new fish showing up each year without having to do any of the work that is recommended in most of the books that are written about koi.

Next install the Pond Pump and Filter


 Pond Liners


One comment on “Pond Liners

  1. lining for pond on said:

    Pond liners are pretty much installed all in the same manner, just be sure you get a gauge thick enough to reduce any tearing

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