Water Behind Liner

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tyler1012000

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Apr 13, 2011
20
Hey everyone,

Looking for some advice on finding the cause of water getting behind our liner. We noticed about midway through the summer that there was water behind the liner. We got a pump and pumped it back into the pool and about a week later we noticed the water coming back. Based on how clear & clean the water is, I'm pretty confident it's coming from inside the pool and it's not groundwater. I went around the pool looking for anything suspicious and didn't notice anything. I then tried the dye test and couldn't find anything that way either. I'm at a bit of a loss on how to find where the water is getting out. The water is behind the liner on all four corners of the pool but seems to be the most in one corner in the deep end. I checked around the light niche but didn't take the light out. I did go down to the bottom and checked around the drain and there is water underneath the liner at the bottom of the deep end also. Any help or ideas is appreciated.
 
Test the ground water for CYA.

CYA does not occur naturally. If the water has CYA then it is coming from your pool. If the water has no CYA then it is ground water.
 
How close are the return jets? how quickly do water build up behind the liner? can you leave the pump is off for a day or two to see if it only happens when the pump is running? If it only builds up when it's running then a return fitting or line is leaking.

Do you have an auto fill? can you shut it off to see if that might be it? water line for a hose or sprinkler near by?

how well does rain drain away from the pool? what is the decking/patio made from? i'll get a little water behind my liner after long periods of rain, mine case is the water gets under the pavers and does not drain away correctly from the slab of concrete the pavers are set on. My slab needs a few more drain holes in it.
 
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So, we ended up having a leak detection company come out and take a look at it. They checked everything including the plumbing. They're certain there's no issues with the liner but did find a leak in the drain line near the pump. We asked if that would contribute to the water behind the liner and they said yes. They plugged the drain line and we pumped all of the water out from behind the liner. However, we're still getting water behind the liner. Is it possible that there was water behind the liner that is continuing to get pushed up as we empty it or is it new water? Thoughts?
 
Water behind the liner is absolutely normally. The ground gets wet when it rains, and naturally flows everywhere. Including into the big hole that your pool sits in. Drain lines in the backfill normally move it away from the pool. If your pool excavation doesn’t have drains, you may have problems. You can dig a dry well down to the bottom of the pool in the backfill and add a pump to evacuate the water.
 
JohnT said:
Water behind the liner is absolutely normally. The ground gets wet when it rains, and naturally flows everywhere. Including into the big hole that your pool sits in. Drain lines in the backfill normally move it away from the pool. If your pool excavation doesn’t have drains, you may have problems. You can dig a dry well down to the bottom of the pool in the backfill and add a pump to evacuate the water.
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This is a lot of water. And we've had the pool for 19 years and have never had this issue. The liner will start to float and you can feel the water a couple days after draining the water behind it.
 
Depending on the type of soil around your pool it could take a while to drain the water from behind the liner. Since it has not been an issue for 19 years, and i am assuming nothing has changed in the landscaping or grading around the pool or neighbors yard, etc in the past few months that the leak is as you say from the pool line. Are you in an area where the water table could have changed and is high and that is where the water is coming from?

If it is from a leak in the line it could take days, weeks, month to saturate the soil around the leak and up to the pool. At the same time it will take time to get rid of the water in the soil. As you pump water out from behind the liner water from the soil will migrate to that area again and again until the moisture level in the soil is low enough that is does no flow anymore.

Do you know what type of soil is around the pool? If the excavated area around the pool and naive soil was back filled with stone (like type 57) its can hold a lot of water if the soil below it is not very permeable. Basically you have a pool within a pool.

For water to build up behind the liner the water pressure out side the pool has to be higher than the water in the pool. If you keep your pool water as high as possible does it stop or lessen the amount of water getting behind the liner? Can you dig a hole near the pool where water is getting behind the liner and see if it collect water?

What type of decking do you have around your pool? If it's pavers over a concrete slab, water may be migrating between the pavers and slab. Failing polymeric joint sand might be allowing more water to get between the pavers and slab before the water can shed from the pavers.
 
Far and away the most likely source is groundwater. I can't improve on JohnT's explanation. If it never did it before something has likely changed in your landscape to allow groundwater to accumulate around your pool

This might help.........water only goes down......never up. So if you have groundwater around your pool, the source is higher, not lower.
 

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Don't forget to look up when wondering where draining issues are coming from. Check your gutters to ensure they're functioning properly and the water is going where it should the next time it rains. (If you have them)
 
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