Why does my tiled shower/tub smell? My shower smells like a sewer, why? There are two common reasons that you could be smelling sewer gas. Reason one that the shower or sink have not been used in a while and the water in the P trap has evaporated allowing the gases are escaping the plumbing.Second would be that there is no p trap installed at all and there for nothing is there to prevent gasses from coming back up the pipe. What should I do? If your bathroom shower or sink has not been used in a while run some water and see if the smell goes away. If that does not work call a local, reputable licensed plumber to have a look at it and discuss your options. Sewer gas is full of methane and other nasty gases that can be very nauseating and dangerous. My …