Pond Liner underlay - what about using sand, old carpet or newspaper?

<p>In our experience it is worth considering the application of sand as the first or base level of underlay for the pond liner. It will certainly do no harm and can be a useful substrate to level off any large deviancies in the ground. For example, when digging you might hit a rock base layer with a couple of hollows - sand can help to fill up such gaps. Sand can also help with drainage if building on boggy ground (though building a pond in an area with a high water table is not recommended - you can get problems with water getting under the pond liner itself and lifting it). However, the danger with sand is that it settles and can disguise potential sharp points that then become problems weeks, months or years later as the pond settles into position. Of course another problem with using sand as a pond liner underlay is that it is impossible to use it on the sides of the pond - even when wet it will simply fall into the bottom of the pond construction. For these reasons we think that while sand can be useful it should not be used in isolation. Use it in conjunction with a good geotextile <a href="http://www.pondkeeper.co.uk/underlay.asp">pond liner underlay</a> sheet.</p> <p>Carpet is sometimes suggested as a pond liner underlay and you might get away with this - just ensure that the carpet is a man-made fibre such as polypropylene as a natural fabric such as wool will rot over time reducing it's effectiveness as a barrier and leaving the pond liner exposed to danger. Just be careful here as carpet will often be a mix of fibres and may even have an underlayment attached. You might end up with an underlay that attracts mold, bacteria and starts to smell. It may even be like this before it goes under the pond if it has already been laid for a number of years as a floor covering. As a final word of caution - if you do use carpet ensure that it doesn't contain any sharp carpet staples or tacks that are used laying the carpet indoors. Such items can cause injury when laying and will, of course, pierce straight through a <a href="http://www.pondkeeper.co.uk/pond-liners.asp">pond liner</a>.</p> <p>Newspaper can be packed together to form a wadding but again it will rot down so you need to make sure it is very densely packed. It suffers from the same 'settlement' problem as sand as discussed. Again, newspaper can be used as a first degree of pond liner underlay but it should be used in conjunction with a proper geotextile pond liner underlay.</p>