What’s The Deal about Pond Liners

Pond Liner, Oh no my pond leaks.
Some types of ground will not have enough clay content to seal, thus the need for pond liners. 
What’s The Purpose of Pond Liners. Seal the bottom and sides, and help prevent erosion.
Depending on your location and the type of soil, there may not be enough clay content to hold water. Typical ground structure is as follows, top soil could be 2 inches deep to 24” deep. This will not hold water, it is porous and should be used for replanting grass around the pond.
The next layer is generally clay, it has finer particles, and will bind together. When dry it shrinks, you may have seen cracks in the ground in the summer, dried out is very hard, harder than top soil, but once it is wet it will expand. This area can be suitable clay and used as a pond liner.
Digging a larger, deeper pond with a backhoe or dozer there could be sand, gravel, even shale that will not be suitable to retain water. The sand, gravel, or shale will act as a drain in the pond. If an unsuitable material is found on the side walls, it could be tamped in with clay.Let’s say you get lucky and find blue clay, this ideal for a pond liner. The texture and appearance is just like what pottery is made of. Get it wet and it is mold able, smooth it out with your fingers and it will have a shiny appearance and stick together. The same test can be done to any of the other layers, get it wet form a bowl and see if it holds water, if it does then there is a good pond liner. Another option is a container, with a few holes in the bottom add a layer of coarse sand or small gravel, then add what is thought to be clay, tamp (compact) on top of the gravel, fill it up with water and let it sit over night. If nothing leaks out it is a good chance its clay or has enough clay content.
Finding that there is only sandy or gravel ground to work with leaves the only option of a pond liner, which can be made from rubber, vinyl or pvc to retain the water.
Another option is sodium bentonite clay. Which will need to be professionally applied as a pond liner. Other sources to seal a pond are Pond Seal, patch a leak or line the pond and check out the strongest Pond Liner available.