Why are there lumps on the outside of our vinyl pool liner?

Question:It's in-ground. We can feel rocks or gravel or something. They're getting worse. Do we need to call someone in? Are we going to have to replace the liner? I don't think it's roots; it seems more like rocks.

Answers:
we had that... it actually was roots from a tree nearby. we ended up replacing our liner, but it was just something we wanted to do cosmetically. i think you're ok unless it pokes through.

it never hurts to call your pool technicians though.