Bumps Under Vinyl Liner

by Amy
(Westminster, MD)

My above ground pool is only about a year old. I recently noticed hard little bumps under the liner around the entire pool just about a foot below the water line. Can you tell me what these are and what I could possibly do to prevent any problems they could cause with my liner?
Thanks.




Hi Amy. That’s not a question I can answer with a definite “this is your problem”, but I will give you some possibilities. Sand behind a liner causes bumps but this is way to high up the wall for sand and it would have been there since the beginning.

It is probably something that is developing, or growing, on the wall. I have seen calcium deposits do this. They are usually caused by water getting in behind the liner from either leaky fittings or a hole in the liner. The wall itself could be corroding in some way. I have seen aluminum walls rust in this way, first causing little bumps and then holes in the wall. On a steel wall it could be the paint bubbling, reacting to something possibly. It is even possible that rust is developing on the wall.

If it were my pool I think I would want to know what it is. You just need to drop the water down about half way and remove a couple of top rails. You can then remove a stabilizing rod or two and get in behind the liner. That should give you some indication about what is going on.