I'm not sure if I have enough information for anyone to help; but here goes. We removed the drywall on the outside wall of the basement corner shower (pipes leaked but are now fixed). After we removed the drywall we were able to see under the corner shower. The base is about 4 inches high and we can see the drain pipe coming out of the floor. The problem is that there is a large hole in the concrete where the pipe is coming out. Looks like the installer tied into the sewer line but didn't fill the hole with concrete. We are just wondering if could be a problem. There has been no water coming up but we can't tell if it is damp down the hole. It is about 1' x 1' in size - do not know how deep. We live in an area with lots of radon and would like to patch this hole up. I think we would have to remove the shower to do so. Any thoughts? Should we just leave it? Could it possibly have a purpose? We want to put drywall back on the wall but don't want to do that until we figure this out. Thanks!