Using a Plastic Liner for the Garden Pond
Place the pond out in the open where possible; this will encourage good plant growth. Allow plenty of space around it for access to the fish and plants. Mark out the area needed and then check the levels; it is very rare to find a garden that is absolutely flat, even if it looks level. The pool structure must lie level and the spoil dug out can be used to build up a ridge to make the liner just contain the water and not stick up at one end.
When digging the pond it is important to incorporate shelves along the sides, at least 20cm (8in) wide and 23cm (9in) below the water surface, to accommodate plants that need just a little water over their roots. The deeper parts can be dug to a depth suitable for your plants and fishes: this should be not less than 45cm (18in) deep. Deeper ponds are needed for Koi, which need water about 1.5m (5ft) deep. Shallow ponds are prone to freezing in winter and overheating in summer, to the distress of the fishes. Remove a strip of turf around the edge, about 5cm (2in) deep and 45cm (18in) wide, for the liner to bed into.
The liner should be plenty large enough and the size can be calculated by taking the overall dimensions and adding double the depth to the length and double the depth to the width. For example, if the hole measures 3.6m (12ft) long, 2.4m (8ft) wide and 60cm (2ft) deep, then the liner should be 3.6m (12ft) plus twice the depth of 60cm (2ft) long and 2.4m (8ft) plus twice the depth of 60cm (2ft) wide, so the pool requires a Iiner4.8m(16ft) by 3.6m (12ft).
The liner needs to be pulled fairly taut across the pool and anchored round the edge with heavy weights such as paving slabs. Water is then poured into the liner, which will stretch with the weight and start to conform to the profiles of the cavity, becoming more tight to the walls as the water reaches the top. The liner edge can be trimmed of excess material to leave some 30-45cm (12-18in) to be covered with turf or paving slabs; the latter can be bedded in a generous layer of mortar.