I have had a sewer oder from the shower drain. The S trap has water in it to prevent this, yet the oder is still coming through. The shower drains and is useful, however, the oder is there every morning.
RD

Most bad oders in bathroom drains come from rotting hair mixed with grease from the soap. Try this. Tonight before you go to bed pour 1/2 gallon of bleach down the shower drain and let it set overnight. Next morning flush it down with a few large pans of boiling water. The bleach will start to dissolve and soften the hair and make it slippery and the boiling water will melt the grease and flush the mess out into the main. Now see if that smelly drain doesn't smell sweeter? Hope this helps . Tom

He solved my year old problem