pondliner - will roofing plastic be OK?

[GiddyGoat]

I have been looking after a handful of tadpoles (and a couple of newts by accident) in a makeshift wildlife pond created in a washing-up bowl in my garden. Everything seems to be surviving OK 3 weeks on, but I want to create a slightly bigger, more appropriate pond. I have a large quantity of heavy-duty roofing plastic that seems perfect, but will it give off anything nasty into the water?

[Monkey Orchid]

The usual problem with using plastic as waterproofing for ponds is it degrades with exposure to UV (sunlight), becoming liable to split or crack. I don't know if this would be an issue with your roofing plastic, it's hard to tell without knowing more about it. Ditto whether or not it might give off any harmful chemicals into the water which could affect plants and animals.

When I have made ponds in the past, I generally used purpose-bought butyl rubber pond liner. But maybe your plastic will be OK. With all flexible liners, I'd suggest the following: after you've dug your hole, pick over it for any sharp stones or roots (anything that might pierce the liner). Then line the inside of the hole with something that will act as a 'cushion' for the liner to go on top of - sand, old carpet or even wads of newspaper would be fine. Next put in your liner. For extra protection, you could cover your plastic liner with yet another layer of old carpet - it will protect the liner from UV and damage. Cover the exposed edges of the plastic liner/carpet with turf, add a final layer of topsoil over the rest of the liner/carpet, then allow your pond to fill with water. Get plenty of oxygenating plants and marginals planted a.s.a.p. and once they've established you can introduce your animals from your washing up bowl.

I've made a few ponds in this way and they've always been colonised pretty quickly and flourished. The only caveat I'd add is if you do use an extra final layer of carpet, sometimes when you add water it starts to lift up and float away from the liner. To deal with this you need to weigh it down thoroughly, e.g. by placing a few large heavy stones or chunks of paving slab (nothing with sharp edges or corners, obviously) spaced at intervals on your liner.

Good luck, Giddygoat - let us know how you get on.

[royden53]

I'd agree that the plastic is likely to deteriorate and will probably crack in 1 to 2 years just at the waterline.
David W.

[GiddyGoat]

Thanks guys - good tips.

I will investigate the heritage of the plastic I have, but it sounds as though the proper stuff might be better anyway, to be on the safe side.

Is just regular soil out of the garden, or compost ok to put in the bottom - anything I should be aware of? (obviously no weed-killer or other sprays in soil)

[Monkey Orchid]

Use ordinary topsoil - but sieve it or pick through it to get any stones out before putting into your pond hole, to minimise the risk of puncturing your liner. Definitely don't use compost - this will be high in nutrients, which is not what you want for your pond. If the pond water gets high levels of nutrients in it, you will get lots of algae growth (turning the water green and soupy).

[tom00_uk]

Originally Posted by Monkey Orchid

Next put in your liner. For extra protection, you could cover your plastic liner with yet another layer of old carpet - it will protect the liner from UV and damage.

there are a lot of chemicals in carpets that will harm aquatic organisms, the are also not that great for land animals but they are added to make them less likely to go up in flames in a fire. if using carpet us under and not in the pond. Hessian sacks can be used in the water, this is one of the ways the EA stabilize river banks, on the Avon the banks were lined with Hessian and then pierced with green willow that would take over holding the bank in place when the the roots grew and the Hessian rotted away.

[Jim Ford]

As you mention slightly bigger than a washing up bowl, how about a 'Muck Bucket' from (say) Wickes? It's not ideal because there is no sloping shallow end for creatures that want to emerge, but you could probably improvise something.

Jim

[GiddyGoat]

Thanks folks - the tip aboout the carpet chemicals is a good one too. There is so much that you wouldn't consider for a moment, that you have to be careful of, but I'm starting to get the idea - take nothing for granted as being safe!

I had heard the hessian idea before which sounds a great idea - you reminded me to get onto Freecycle and see if anyone can give me some hessian they don't want.

I now have a very big hole dug and I'm getting awfully excited!

[Monkey Orchid]

Originally Posted by tom00_uk

there are a lot of chemicals in carpets that will harm aquatic organisms, the are also not that great for land animals but they are added to make them less likely to go up in flames in a fire. if using carpet us under and not in the pond. Hessian sacks can be used in the water, this is one of the ways the EA stabilize river banks, on the Avon the banks were lined with Hessian and then pierced with green willow that would take over holding the bank in place when the the roots grew and the Hessian rotted away.

Good point about the chemicals, I was thinking more of using the ethnic-type carpets (thick cotton rugs) rather than artificial fibre carpets. An acquaintance of mine who has built many ponds used to lie turf on top of his pond liners: he would cut it from the site the pond was being dug in, line the hole with sand or carpet, put down the liner, then lie the pieces of turf grass-side down on top of the liner. They would hold in place nicely on the sloping sides of the pond, then he'd put a layer of sieved topsoil on the bottom. Around the edges of the pond he would also cover the liner with turf, but grass-side-up in this case (to form a natural edge). This way the liner was completely covered with natural materials.