Water under liner while building


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I have a hole (not a pond yet), 23x30ish. I put down underlayment and the the liner.
The liner is big enough that it covers the berm all the way around and we'll edges are on the down hill outside and we held down by rocks.
The berm is at least a foot higher than surrounding ground all the way around, higher in most places.
I can see no way water could have gotten underneath the liner, but I've got two feet of water under the deep section after a lot of rain.

There are no rocks placed yet, no water in it other than what gathered with the rain, but when I went to start building up rock I stepped in and sank in the liner because of the large pool underneath.

I can't figure out of this is a big problem or if I had a full pond it wouldn't have collected there, but I'm ready to smash my head into the rocks over it.

I'm at a loss as to what to do. I'm pumping out the water, but if it's going to bubble up once I fill it I've got a problem that I don't know how to fix.

Unless someone can convince me it's just because the pond is empty and water seeped in that wouldn't were it full.

Please help. I'm at my wits end with what to do.
 
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brokensword

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@GBBUDD is the pro on this subject, but I believe the solution is to establish a pipe UNDER your liner and have it ported/vented out one side by running it vertically above the pond height. The idea is that the water will collect in this under-liner piping and the natural pressures will force it up and out because it's the path of least resistance now, thus no collecting beneath your pond liner. This is probably happening because the water table is higher than you want it. If I'm wrong about the above fix, GB will correct it. Btw, when this happens, it's called a 'hippo'. Don't ask.
 
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Agree w/ @brokensword. Sounds like high water table. Imagine right now is the highest it will ever be and pressure from rocks/water once pond is full MIGHT fix it, but that's a big gamble.

Believe best solution is to install a french drain across the area in question leading to a sump pit/pump. There are some good videos on Youtube about how to do it. I think the Team Aquascape channel just did rec pond where they had to do this. I remember them showing some of the details of the installation.
 
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As @brokensword mentioned you want to give the water underneath a easier path then it is to build up under the liner. This is done like mentioned above with very similar to a French drain but you should not need a pump expecialy if you are adding stone in the pond when water below the liner and water above the liner meat for lack of a better word the pressures are very similar even with rubber between them . So the empty pipe is less pressure and the path of least resistance. The exit however does not and actually should not be higher then the pond it's self as that will add head pressure for the water to have to build up in order to get that high. Let's say your ground slopes away some 10 feet away from the pond I'd run that discard pipe to that area pitched so the water will run on its own. For a larger pond you may need to make a baffle of pipes across the bottom it all depends on your soils and how much water you get. There are commercialy made drain tiles made, some of your better pond stores have these I do know underwater warehouse sells one type . But it is a real dyi possibility as well with just some perforated pipe. Just make sure it can take being buried and that it's not going to collapse and ruin your efforts.
 
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j.w

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@conley2112
Good info given and hope you can get that hippo taken care of!
 

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