Getting your pond lining material right is essential
Every man-made pond, water garden or stream begins with good quality pond liners. The pond lining material must be durable enough to keep water from seeping into their dug-out foundations and yet be made of material friendly to aquatic life.
Before selecting pond lining material it is first necessary to determine the size of your pond.
The formula for calculating Pond Liner Size is as follows:
Pond Liner Length = Pond Length + (Pond Depth X 2) + (Overlap X 2).
Pond Liner Width = Pond Width + (Pond Depth X 2) + (Overlap X 2).
When laying out your pond liner it is advisable to allow for a 1-2 foot overlap that can be trimmed or hidden after lining contours have been laid out flush. Pond depth for Koi ponds is recommended to be 3-5 feet deep.
Once you have your pond’s square foot measurements determined, you can figure out the correct thickness your pond lining material should be. Thickness is measured in “mil” in the US. Specifically, this means 1/1000 of an inch. The thicker the liner, the heavier it is. While thickness may mean a more durable pond liner it also makes it less flexible, more expensive and more difficult to install. The thickness of pond lining material recommended for Koi ponds varies from 20-45 mil.
Currently, there are five types of pond liners commercially available. They are made from either rubber or plastic.
The most popular rubber pond lining is called EPDM (Ethylene-Propylene-Diene Monomer). It is available in varying degrees of thickness and is known for its malleability as it is easy to install. It can withstand temperatures of -40 to 79 degrees C (-40 to175 degrees F) but is also the most expensive option. Good quality EPDMs such as those made by Firestone come with a 20 to 30-year warranty.
EPDM’s UK counterpart is called Butyl Rubber. Chemically, EPDM and Butyl are different synthetic chains but they are both structurally the same and used for similar purposes (such as pond lining) in each region.
Polyethylene pond liners on the other hand, are stiffer (being plastic based) but cheaper than others. This is an ideal choice for large scale pond projects such as those for parks where material needs to be durable, UV stable (not destroyed by UV exposure) and safe all year round. It can be used in temperatures ranging as low as -56.6 to 82 degrees C (-70 to 180 degrees F)
HDPE (High-density Polyethylene) is another plastic liner which comes in 20 or 40 mil thickness. It is less expensive than EPDMs and less malleable as well. It comes with a 20-year warranty and is UV safe.
LLDPEs (Linear Low Density Polyethylene) are less dense than HDPE’s. Therefore they can be more prone to puncture but are more flexible when used to line ponds. These are available in the US and South Africa.
The cheapest of the plastic-based pond lining materials is the PVC (PolyViny Chloride) which generally carries warranties from 2 to 10 years. While it is very malleable and lightweight, this polymer is not UV stable, nor is it as durable as the rest. However, repairs for this lining can be done underwater.
Whatever pond lining material suits your needs, it is recommended to use an underlayment made of non-woven soft fabric beneath it. This is to ensure that your lining is not punctured by sharp rocks on your pond bed. Underlayment is also commercially available. Interestingly enough however, and perhaps to save on costs, some Koi pond keepers have used old carpet padding for this same purpose!