Pond liners: preparing the ground
Laying the pond liner is a big step in the pond construction. Pond liners are commonly either preformed which are rigid or Butyl which is a flexible material liner. This next step is optional but highly recommended if you intend to line the pond with Butyl as compared to a rigid preformed liner. Butyl Pond liner is tough, however, the weight of water creates pressure on the liner and if the liner gets breached or holed in the future, it creates a massive problem of a leaking pond. To minimise this it is a good idea to line the area before laying the Butyl liner with a specially made protective fleece to preserve and prolong the life of the liner. The ponds illustrated in the images were built in ground that was very rocky which required extra work and attention when lining the pond with Butyl liner. If you have soft sandy ground this will not be essential; rocky flinty ground you may want to consider a soft liner before the Butyl to give extra protection.
For a long lasting pond you can also cement in the shell once the hole has been dug, levelled and shaped as in the image. Whether you take this step will depend on the ground in which you are constructing the pond. In the image the ground was flinty and it was not possible to shape the soil to the degree that was needed for the planting shelves. Rocky ground doesn't really hold a shape well so it was better to cement it. On these pages are ideas for building a pond, but it will, as always depend on the ground as to what work is needed; some soil is easier.
Butyl liner is flexible and can be made to the shape of your pond. It is quite heavy and best laid out on a warm day to make it flexible and malleable . Start from the centre and lay the liner outwards. The aim is to get it as flat as possible and run it up to the top of the pond and just over onto the ground, bearing in mind the need to hide the liner to ensure the
finished result looks professional.
Preformed liners are made of plastic or glass fiber and are rigid, long lasting and need to be fitted exactly into the hole and level.
For all ponds level is crucial: it is worth spending time levelling the pond because if you fill up the pond at the end stage, and it is not level, it will show. Water will find the level and it will look odd. A spirit level needs to be used to check the pond at the bottom and at all points to ensure it is 100% level before fitting the liner.
A butyl liner needs to be laid from the center of the pond outwards pleating carefully on shelves to get the liner as flat as possible.
Retailer web sites explain how to calculate the size of pond liner needed for your intended pond. Liner is expensive as are any mistakes if there are miscalculations. Good retailers will assist in the calculation if you call them with the pond dimensions.
Fill the pond before trimming off the liner. Use bricks along the rim to hold it in pace and then fill, settle and then trim off surplus leaving an overhang which will need to be disguised with plants and stones.
You are then ready to fill up the pond with water. Initially for a short while it will be clear and then turn green. It will take time for the natural balance of the eco system in the pond to return the water to clear. Although in the first instance the only practical way to fill the pond is to use tap water if at all possible after that fill and top from a water but using natural rainwater.