Sink Holes??

I think I know the answer to this question, but I'll post it anyway - in hopes someone has a better (easier) idea.

We have discovered a "sink hole" below the liner near the edge of the pool. The hole is about 2 1/2" deep x 4" wide. I figured we would just have to live w/it, until we found another area, about 3 feet away from this one, toward the middle of the pool. This sink hole is more of a crater that measures about 2" deep by 12" long.

So, I'm guessing one of three things occurred that caused this...
1. 3 weeks ago we experienced about 9" of rain in less than a week.
2. I was adding water to the pool one evening, forgot about it, and woke up the next morning to find water spilling out of the skimmer.
3. There's a small hole in the liner which is allowing water to seep underneath, causing the sand to give out.

Solution: The only thing I know to do is drain the pool, leaving a small amount of water - add more sand underneath the area and refill w/water. I read where one "expert" recommended placing sheet metal under the area, then sand on top. I'd be concerned the sheet metal would puncture the liner.

I'm at a loss with which direction to go. I can leave it as is, and see if it gets worse, or try and be proactive and take action to lessen any further erosion underneath. I spent a great deal of money having this pool installed and the crew took half a day leveling & adding sand to make sure this wouldn't happen.

Any advice would be greatly appreciated.

Could it be a mole or a vole?

I would see if they get any worse, but as you said, emptying and filling with sand is the only real repair. I dont know about the sheet metal though.

If its from heavy rain, you may need to divert the runoff so it goes around the pool.


I just replaced the liner in my 24' and right before I was putting the liner in I had a few mole /vole trails coming in from the edges (this year I have a big problem with them all over my yard). I put down some repellent pellets, smoothed the sand and put the new liner in.