 Are you sure it's coming from that shower drain? Yeah, because I put a thing over the drain when I'm gone and I don't have the smell. It doesn't happen all the time, but about 80% of the time I get the smell. Okay. But if I put something over it, what I do every day, I put something over it so when I come home I don't smell it. So here's what's happening would be my guess. Something is sucking the water out of the trap