OK, so I don't have a lot of experience with plumbing so I hope there's a simple fix for this and I just don't know it! I just bought a house and the previous owner had the bathroom completely redone. There was no shower there three years ago so I know everything is new. The problem is that she tiled the floor once and then tiled over it...now the new tiles will not stay in place. Every time I use the shower (which has been about 5 times...thank goodness there's a separate tub!) grout and adhesive come up between the tiles. I would most like to remove the entire second layer of tiles (because the first layer is the exact same tile) but then the lip of the shower drain is about 1/4" above the floor level, meaning there'd be water standing on the floor. Any suggestion, anyone? Thanks.