Sinkhole in Pool?? Help...

[pumpkinbugs]

Ugh... So last summer (2015) we had an 18'x36' vinyl in ground pool installed with completion of the pool in August. All has been going fine until I noticed one of the long sided walls (36' side) seemed to have dirt behind the liner (between the steel wall and liner) which was not present before. In addition, my daughter discovered a sinkhole in the deep end of the pool where the angle of the drop meets the bottom of the pool. The bottom of the pool is made with vermiculite. The sinkhole is about 5-6" across and 2-3" deep. We are so disappointed. Not sure if this has anything to do with it, but about a week before we noticed all this, we had a large amount of rain that filled the pool to the brim. Could water be getting behind the liner? I've contacted the pool builder, but so far no response....

 

[gwegan]

You have high groundwater. Water from the surrounding soil is getting into the pool structure. With vinyl pools it is extremely important to keep water away from the pool.

First you are going to need to install either dry wells and a pump system to keep the area dry when it rains and or french drains to do the same. A good pool contractor should see this and take precautions. But at the minimum you need a good landscape contractor to come out and offer some solutions.

Second, I suspect that's no a sinkhole but a collapse or shift in the dirt under the pool surface caused by the high water table. You can either fix that or live with it.

Fixing requires draining and removing the liner and there are problems doing that.

 

[pumpkinbugs]

We live in an area that has lots of clay - and the pool was installed in a clay area. However, one note to make (not sure if it makes a difference) - when they were installing the vermiculite, they did it in sections. They started at the shallow end and let it dry for a couple days. When they did the deep end, they didn't even give it 24 hours to dry before the liner showed up. When I originally asked about how long it takes the vermiculite to dry, they said a couple days. I asked why they were putting in the liner in less than 24 hours of allowing the deep end to dry and they said the liner was already scheduled and it should be fine. Do you think this could be a cause?

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We live in an area that has lots of clay - and the pool was installed in a clay area. However, one note to make (not sure if it makes a difference) - when they were installing the vermiculite, they did it in sections. They started at the shallow end and let it dry for a couple days. When they did the deep end, they didn't even give it 24 hours to dry before the liner showed up. When I originally asked about how long it takes the vermiculite to dry, they said a couple days. I asked why they were putting in the liner in less than 24 hours of allowing the deep end to dry and they said the liner was already scheduled and it should be fine. Do you think this could be a cause?

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Sorry, one more question. You mentioned that "Fixing requires draining and removing the liner and there are problems doing that.". What kind of problems to you foresee? Thank you so much!!!

 

[gwegan]

If the soil is still saturated with water around the pool that could cause problems with the pool walls. Right now the water in the pool is supplying back pressure against the walls. If the soil is saturated the walls and pool are no longer in equilibrium and you could have wall bowing or a collapse.

I would have waited a week for the vermiculite to dry.

Your main problem is the ground water. You need to make sure that is removed first.

 

[swimcmp]

We have installed vermiculite/Portland cement for 35 plus years. When we first started doing it we installed vinyl over it the same day. Now we usually install vinyl the next day. I am guessing what has happened is that they had a deep spot that they filled in with clay and since the heavy rain it has settled. When the clay settled it allowed the pool base to drop. We had a similar situation a couple years ago. We drained water out took the liner loose and did the repair to the pool base then immediately started refilling.

 

[pumpkinbugs]

Thank you for the information. What should I expect from my pool installer regarding the pool itself? Aside from the caved in spot, there is also debris behind the liner. I have a feeling he will do nothing about it. Is it too much to ask to drain the pool, fix the caved in spot and remove all debris behind the liner?

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Thank you for all your information. Once we figure out and fix the ground water situation, is it too much to ask the pool installer to have the caved in part of the pool fixed and the debris behind the liner cleaned out? How long can a pool liner go without water?