Materials for Creating and Lining Garden Ponds
Laminated Reinforced Nylon PVC
The most expensive of these materials are strong enough to support water in a pool of almost any size, and it could be constructed by welding the edges together. Cheaper materials in this range would be quite suitable for a pool of any size up to 100 square feet. As these materials are to a greater or lesser degree flexible to calculate the amount of sheeting you need, add twice the maximum depth of the pool to the maximum width and the maximum length. Thus a pool of 9 feet by 6 feet by eighteen feet would require a piece of plastic nine feet by 12 feet.
It is always assumed that irregularly shaped pools require a piece of plastic sheeting corresponding to their maximum length and maximum width calculated as above. Remove any protruding objects in the excavated hole, line with sand, stretch the material with a slight sag in middle over the pool using the edging stones to hold it in place, then gently allow the water to run in. Trim round the edges allowing a sufficiently wide margin to be weighted down by the edging stones, but do not make any nicks which might lead to splits.
This is the most long-lasting and elastic, but also the most expensive of the flexible materials. As it does not wrinkle it is often used for unusually shaped pools. It has one snag, plants have been known to pierce it, and this danger increases the more it is stretched.
This is less long-lasting than the materials mentioned above, and the pool should never be drained, as this exposes the polythene to the weather for long periods, which causes a rapid deterioration in the resilience of the sheeting. However, it is the cheapest buy, and is best suited to formal pools of regular shape as it does not stretch much. Use double thickness 500 grade and allow a shallow 30° gradient to the sides. Take the measurements by tracking down the sides and along the bottom for both width and length and allow an overlap of twelve inches all round so that the edges can be folded over when weighted down.
Pre-shaped Plastic Liners
These are purpose-made and may be either flexible or rigid. In either case the pool must be dug to the dimensions for which they are designed. The rigid ones are the most expensive, in some instances costing as much as four times the price of some of the more flexible liners. However, the small rigid fibreglass or sophisticated plastic pools have a definite value in constructing intricate watercourses with waterfalls, and so on.
In some instances they have lips which may be used to make systems leading from one miniature lake to another, or they may be made in sections which can be fitted together in all sorts of shapes and sizes (the joins must be scaled, however). It is possible to make rigid plastic liners in the excavated hole using polyester resins and hardeners. However, this really requires some previous experience in making laminates.