I have sewer smell coming from my shower drain. There is nothing plugged and the water heater is new (we have tried other water in the house, no smell). When we flush the toilet in this bathroom, there is gurgling in the pipes and when we watch the shower drain, the water level goes down, then bubbles a little and fills back up. This is when we smell the sewer smell the most. Also, when we shower first thing in the morning, the smell is bad. We had a bunch of water leaks (frozen pipes) from this bathroom when we bought the house 4 months ago and had them all repaired. Is this related? How do I fix it? Please say I don't have to tear into the ceiling below it - I just had it re-drywalled!!!