Leaking pond liner

Hello all. Opinions please on relining my fish pond as the liner is leaking, I’ve drained the pond twice & patched anything that looked like a possible leak area, using the extremely sticky patches from our Koi centre. But it’s still leaking app 12” in 24hrs then it slows down, presumably as the water pressure is lessened on any holes etc. We’ve only been in this house for less than 2yrs & the pond had been abandoned & was a mess, so I reinstated it after cleaning & then adding fish, pumps filter etc. All was fine for a while then suddenly the level dropped & is still dropping even after doing the above exercise. Believe me, with the pond drained & dried, I’ve gone over the entire area checking again for possible leaks. Even injecting compressed air twix liner & pond walls as I slowly refilled. Not a sign of any air bubbles! So the question is whether to use a Butyl or cheaper lining, as it will be laid over the existing one. Obviously I’ve no idea what type of lining it is, but it’s quite heavy & I’d say the thickness is 1mm from the feel of it. I’m more than certain there is no underlay, but the existing liner would suffice to do that job? Any comments gratefully accepted. Sorry for the saga length post.
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Right, stupid question time! Are you sure you have a leak? My pond looses loads of water at this time of year, i assume its a mixture of evaporation and the plants in the pond growing strongly! Ive heard ofthers say this too
Hi bekkie
That was my first thought after the 2nd attempt to find a leak, but a 12" drop in a day is a helluva lot of evaporation. I'm in West Yorkshire not "Death Valley"
I have just loaded a marvelous little book onto my kindle by Alex Sally who builds large ponds for wildlife areas parks etc, he is very knowledgable, its a very good read, but apart from that, there is a link at the end of the book for a company selling liners and the underliner giving 10% off. It worked out much cheaper than Amazon and was delivered very quickly post free. Thats if you are looking to buy a new liner. Also, if you use their recommended underliner, it is guaranteed for 35 years, The company is called Bradshaws Direct.
@ pansyface, I agree, there's obviously a leak, but remember I had compressed air being pumped in as I refilled?? If I do fit another liner & it's leaning that way, the decision is whether to rip the old out, or leave it in situ using it as an underliner, in which case I'll never know where the leak was, which is infuriating. With regards to allowing it to find its own level. The problem there is as stated in my OP, with the pressure diminishing as the level drops, it could actually stop leaking because the remaining pressure isn't enough to find its way through. So the actual leak area could still be lower down.
@ Lyn, thanks for the book link.
The fish have put some weight on since I bought them, hope they realise they're just supposed to swim in the water, not drink the stuff
Yes bekkie a lot of work lies ahead & a lot of plants are going to be lost. The back of the pond is formed into a waterfall course with ivy, marsh marigold & bulrushes. I'm not looking forward to this job. Thanks all for your input.
@ pansyface, I don't think that's an issue, as when cleaning the liner, the base was very firm. To be certain that the firm soil under the liner was not restricting the air flow during the test, I put app 8" back in the pond, which allowed me to then grab a hold of the liner one side at a time & lift it so the base & water where now sloshing about allowing air access to the very underside of the liner. Then continuing to inject air as the level slowly rose. That's the infuriating part of the whole problem. I don't suppose many people have the facility to do what I was doing ie injecting compressed air. But even doing that, the result suggested there are no punctures. I am stumped
Are your German Shepherds called Florence and Fred?
Hi Lyn, I've rescued & retrained 9 Shepherds since my wife & I rescued our first one in '66. The one in my avatar is "Our Cassy" & who passed away in 2012, & my final one. I lost my wife in 2010 so my life has taken a massive turn round. Re-married & now living in Yorkshire. But back to the pond, I've posted a pic of the drained pond & decided to grasp the nettle & make a start. I'll post up when??? I get it sorted.