Depending on how the drain was installed, the trap may have been removed and not replaced, or the new drain may have been connected to the old trap and the piping is getting a coating on it which is giving the odor. If your problem is due to either of these conditions then there is no solution without removing the shower or at least part of the floor.: We recently installed a standing shower stall in an existing bathroom. We took out a tub and replaced it with the shower. There is a very strong sewer smell coming up from the drain in the shower. What have we done wrong and how do we correct it?