Indentation in side of vinyl liner

[cnshough]

Just noticed there is a spot larger than a softball that is sunk-in about 2 ft from the top of the liner. The liner is only 8 months old. Doesn't seem to be losing any more water than usual. Any ideas what the problem could be, and what needs to be done?

EDIT: The indentation wasn't there in August. It's right below the diving board, almost dead center of the pool. Could there have been a light there at one time, and when the previous owner replaced the liner, they just covered over it?

 

[Isaac-1]

could be a sink hole, these are common problems depending on soil condition, I have one that slowly keep growing at the shallow end of my pool right at the base of the steps, it is now about the size of my foot, started out about the size of my thumb around 5 years ago. Liner is now about 10 years old, Sometimes these will be associated with a leak, and sometimes the will not, you can test by carefully squirting some red food coloring in the water around the indention as see if it gets sucked out, move slowly so as to minimally disturb the water.

 

[swimcmp]

Yes it could be a light niche opening. Sounds about the right height on the wall

 

[Bama Rambler]

I agree that it sounds like the perfect spot for and old light. Since it's only 8 months old you can drain the water to just below it and pull the liner out of the track and see what's going on. The installers may even be willing to help you with it.

Depending on where you're located you may want to wait until it's warmer weather.

 

[Isaac-1]

I agree now that you have added the location as being under the diving board, sounds like an old light niche. Perhaps they covered it with plywood of similar and the water pressure is now causing it to cave in.

 

[cnshough]

I talked to the previous owner, and she said she thinks there was a light there at one time. So, what now? Why would they just cover it? How can I put a light back in it? What about cost?

 

[Bama Rambler]

They most likely had a problem with it and decided it wasn't worth the trouble to fix it. Maybe they never used it.

To put it back might be a pretty good undertaking, depending on what was wrong originally. You may have to tear up some decking and run new conduit. As well as install the niche.