Hi. I'm new to the forum and am looking for some possible advice regarding an unusual plumbing problem I experienced a few days ago. I have a toilet and shower down in my finished basement. The other day my shower drain backed up. The unusual part of it is that my bathroom floor didn't get wet but the carpeting outside the bathroom shower got contaminated with sewer backup leaving me to wonder how the carpeting outside the shower area could get wet but not the bathroom floor itself. There is a 2" lip on my bathroom shower opening where you walk in to it. I can only assume the backup must have penetrated through bad grout or caulking when the water rose in the shower. In any event a plumber came out and roto rooted the main sewer drain to the street. He seemed to think that would take care of it. Yet I'm still wondering how an area outside the shower could get wet but not the bathroom floor. The plumber thought there might be a chance that the shower drain wasn't put in correctly or there is possibly a leak in the shower drain pipe itself, which would be an expensive repair. The pipe must run through the concrete floor of my basement. Any thoughts on this? The shower isn't used that often but when running the shower the other day, nothing unusual happened.