Trapped Air Under Liner? Help!

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Any time we get significant rainfall here in GA my pond turns itself inside out and pushes most of the water out of the pond. It only happens when there is a lot of rain so maybe 3-5 times a year. So far it's happened twice in 2025, so I wonder if it is getting worse. It is very squishy and feels like trapped air under the liner. I am meeting with contractors to address drainage as it does run down hill and my entire back yard get wet. I met with one drainage pro today and he could not explain what was happening, but maybe water was somehow coming off the hill and getting behind the liner. Any one dealt with this before?
 

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Three to five times PER YEAR? Yikes! You never want a pond built where the water drains towards it - but here you are.

You have a water hippo. You need drainage under the pond to get the water out before it builds up pressure. Could be as simple as a drain pipe to give the water somewhere to go or you may even need a sump pump under the liner. How a water drainage “pro” couldn’t figure that out would give me pause - find a new pro.
 
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You also need to divert the water that is running under your pond. There is no need for that to happen in the first place if your pond has the proper drainage around it. And yes, you definitely need a new pro.
 

addy1

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My ponds are at the bottom of our steep slope. No water hippos, ever happen.

BUT while building I went out with every rain storm, watched the flow of the water down the hill. Everywhere it was flowing towards the pond I built berms. They have diverted the rain water flow for the past 15 years.
 
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My ponds are at the bottom of our steep slope. No water hippos, ever happen.

BUT while building I went out with every rain storm, watched the flow of the water down the hill. Everywhere it was flowing towards the pond I built berms. They have diverted the rain water flow for the past 15 years.
Exactly - divert the flow. Don’t let it flow to the pond.
 
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Any time we get significant rainfall here in GA my pond turns itself inside out and pushes most of the water out of the pond. It only happens when there is a lot of rain so maybe 3-5 times a year. So far it's happened twice in 2025, so I wonder if it is getting worse. It is very squishy and feels like trapped air under the liner. I am meeting with contractors to address drainage as it does run down hill and my entire back yard get wet. I met with one drainage pro today and he could not explain what was happening, but maybe water was somehow coming off the hill and getting behind the liner. Any one dealt with this before?
Firstly you definitely need to keep looking for a Qualified pro.
Building berms around the pond/ building up the sides keeping run off from getting to the pond is a must. Whether the water goes under the liner or into the pond is baddddd. Unless you live on cape cos and you have nothing but sand and the water will drain away long before it can build up pressure.

Three options the first was just mentioned second is to dig down on the sides of the pond down toward the bottom in the spot where you always see the hippo start first. Get to the bottom along the side" this is after you drain the pond" and install pipe pretty much any pipe that will not crush in backfilling. Pipe goes to the bottom but sits in a pocket of stone that will not plug up the pipe . This creates a path of least resistance. A place for the water to rise instead of raising your liner within the pond. You can do this in several spots around the pond.

Lastly is dig a pit again next to the liner. Make a larger pit so you can make a sump area for lots of water to drain into a bucket surrounded by stone and a sump pump. This should get at least a foot deeper than your pond.
Good luck.
 
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I did not spell out that the pipeneeds to go from the bottom the source of the water to the top of ground level or where you can drain the water away from the pond
 

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