Any pond is only as good as its liner. In the end how well the pond holds water – and how long it lasts – really all comes down to the material used to line it in the first place. Although concrete and puddled clay are sometimes used very successfully, for most would-be water gardeners, the choice is usually between the versatility of flexible liners or the ready appeal of pre-formed ones.
Pre-formed pond liners come in a variety of sizes, shapes and materials and offer some advantages over flexible liners, chiefly in that they do not have unsightly creases and folds and all the planting shelves have already been incorporated into the design. On the other hand, though they are strong and not prone to springing leaks, depending on design they can sometimes be awkward to fit perfectly, are not easy to transport, do not weather or naturalise particularly well and are generally limited to providing relatively small ponds. However, for some applications they can be well-nigh ideal.
Materials and Advantages
The principal advantage of pre-formed ponds are that they offer an almost instant solution to creating a pond – all that is needed is to pick one of appropriate size with the sorts of planting shelves you want and then dig a hole to fit. With the large range available, finding something to meet your needs should not be difficult, though often it may need to be ordered as few garden centres or pond suppliers carry a huge stock.
Fibreglass ponds are generally highly durable and provide the larger sizes of pre-formed liners and are typically fabricated with a number of planting features built-in. They have the greatest life expectancy of all the pre-formed liners and are usually available in a wider range of colours too, making it easier to blend them in to their surroundings. Alternative materials, such as ABS and HDPE are robust enough for most uses and considerably cheaper than their fibreglass counterparts, though they are only available in relatively small sizes. The smooth sides of most of these pre-formed ponds makes them easy to clean, but at the same time, they never weather to appear entirely natural – even if they are well planted, there is always a look of the pre-fabricated about them – though for some gardens this need not be a problem.
Using a Pre-Formed Liner
Modern pre-formed liners are sturdily built and easy to install. Creating a pond with a pre-formed liner is a relatively simple DIY project and can usually be completed in a single weekend, though it is essential to make sure that the liner is sitting correctly and is fully supported.
The trick to creating the perfect pond with a pre-formed pond liner is to dig the original hole to follow the contours of the moulding as closely as possible and then evening out any gaps with the protective layer of sand and finally adjusting it so that it sits level. Some back-filling will probably be necessary to achieve this, but ideally it should be kept to a minimum to guarantee the greatest possible support for the liner.
While they may not last as long as ponds made from butyl or EPDM, if the preparatory work is done properly, they should survive for ten years or longer. Although they have their limitations and cannot offer the range of tailor-made contours possible for a flexible liner, they are available in a range of sizes and shapes, offering a relatively quick route to a perfectly serviceable pond.