I have noticed that there is a rotten egg smell in the bathroom after taking a shower. The problem only occurs in the evening. At first I thought it was the crud that builds up in the sink drain from toothpaste & soap so I cleaned the drain pipes. I also cleaned the overflow passages in the sink. I got a lot of crud out of it but the rotten egg smell still persisted. I checked the shower drain pipe for evidence of crud and it was clean.
Since the cost of a wax ring is low, I pulled the toilet, cleaned under the mounting surface, and installed a new wax ring. No water leaks but the rotten egg smell still persists in the evening when the shower is used.
Last evening, the shower in question was not used - rather a different one in the house was used. The rotten egg smell in the first bathroom was evident but not in the bathroom where the shower was used... I am starting to think a vent pipe through the roof is plugged up but the drains all drain fine and do not exhibit the "blub, blub, blub" sound like a vent is restricted/pluged.
The house has city water supply and a septic system.
What am I overlooking?