Ponds can be lined in several different ways.

• By screeding the inside with a thick layer of cement that is then treated with a painted on waterproofing system or by actually coating with fibreglass. This is usually seen on very large koi ponds. This is a good strong and very permanent method but repairs can be difficult and great care in design and construction is required because of the great weight of water it must retain.

• Preformed plastic ponds, these are very strong and not likely to form leaks. They can be difficult to fit due to their varying shapes and depths sizes are limited to fairly small ponds. And getting them home will probably incur extra expense. Preformed ponds are usually expensive.


• Flexible Sheet Liners made from pvc or rubber vary greatly in quality buy the best you can afford butyl is probably the best but basically the thicker and more subtle the better as cheap liners easily develop leaks. An underlay bought as such or old but not woollen (it rots) carpet is required to protect from sharp stones roots etc, a thick layer of sand also acts as a good underlining.
  

These flexible liners come with warranties, which do imply their quality but normally only cover faulty seams and UV damage, also removing a liner once fitted to have it repaired is not a simple task. Flexibility, cost and simplicity are the main benefits of these liners; they are also easily repaired once a leak has been found.