London (change)
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03/07/2014 at 20:57

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.

03/07/2014 at 21:10
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
03/07/2014 at 22:16

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"

03/07/2014 at 22:46
You have a leak. Somehow. The way to find out where it is would obviously be to let it go on leaking until it stopped and then you'd know the level it occurred at at least.

However, if you have fish and so on that's not really an option. We have had two leaks in ours over five years and both happened suddenly. One was a heron that stabbed a hole in the butyl. The other was when a vole dug away the soil under some edging stones, sharp ones, and one fell into the pond during the night.

We bought more butyl liner, bought lots of those builders bucket things and some sand. Emptied the pond contents into the builders buckets. Lots of wildlife got crushed or killed, sadly, despite our best efforts. Hoiked out as much as we could save. Took out the old liner. Poured sand in to make a bed for the new liner. Cut it to size and fitted it. Let it sit for a while then filled the pond slowly, easing out the creases. Let it sit overnight before filling it with old, saved pond water, water butt water and treated tap water. Added wildlife. Waited. Since the latest disaster it has taken about three months for things to return to normal.
04/07/2014 at 01:58

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.

04/07/2014 at 07:00

@ 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. 

04/07/2014 at 07:10
Well it must be a leak. It's not evaporating at that rate. No thirsty elephants in the garden. It has to be draining away.
04/07/2014 at 07:28
What a shame, and such a lot of work, i dont envy you! I probably would use the old liner as an under liner
04/07/2014 at 07:49

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. 

04/07/2014 at 07:52
As I was thinking about reusing the old liner and thinking that it might not be advisable because the lost water will have washed away the underlying soil and changed the profile of the base, I wondered if there could be a broken drain or a burst water pipe that has caused the thing to cave in. A bit of a wild idea but it might account for the lack of bubbles with the air test?
04/07/2014 at 09:24

@ 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

04/07/2014 at 09:52

Are your German Shepherds called Florence and Fred?

04/07/2014 at 10:35

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.

04/07/2014 at 10:40

Hello gsdf&f.

Check around the perimeter of the pond at the level that the water has stopped dropping for any visible holes or tears. 
If none are visible, you must top up the pond with an inch or two of water. 
Then gently pour a cup of milk or condensed milk as close to the centre of your pond as you can get). It should be sucked toward the leak and you will be able to see the white milky trail. 

If you see no trail from the centre, try adding milk to areas around the perimeter. Pour It around the edges, maybe a short distances at a time.

You can also try  cornmeal!  It gets drawn into small holes and swells and then possibly binds with fine soil particles under the liner and stops the leak but you will have to watch for the point where the cornmeal is going to.

The best way is to lower the water level to about six inches below the leak (stop point). Get in the water or put a ladder over with planks on and go slowly around the edge with a sponge and cloth, rubbing and drying and looking, up close. Even if it's a pin-hole you will see it. Moisture comes through from the backside as you wipe/dry. look for little tiny beads of moisture showing up on dry areas of the liner where soil moisture is moving through small punctures.

Both the milk and cornmeal method are fish friendly.

Hope this helps.




04/07/2014 at 10:57
Thats very clever Edd!
04/07/2014 at 13:24

@ Lyn, doh! the penny's just dropped, (gsdf&f), Florence & Fred  Then I go on to give you my life story. Sorry, just a senior moment.

@ Edd wow! that's involved, but no disrespect to you, but have you read all my threads?

04/07/2014 at 14:06

I have a sneaking suspicion the leak is under one of the folds gsdf&f. When you are trying to forcing air through at the underside and you have the weight of the water inside you might be temporarily sealing the leak. If you get my drift. A bit like applying pressure to a open would to stop the bleeding.

04/07/2014 at 14:33

Thanks Edd, I'm in the process of letting the water level fall again, but this time I'll try opening the folds, & there are a few of 'em, whilst injecting air, fingers crossed.

04/07/2014 at 14:45

No probs, I am so pleased your life has been turned around and you are happy again.

I hope the pond gets sorted, I have a liner waiting for a hole.

We tried a pre formed one, but what a bugger to dig all the contours, my OH has no patience, at least with a liner it fits whatever you have dug.

04/07/2014 at 14:56

Could it be leaking out in your waterfall area? My first pond had a leak there and it took forever to find.

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