My mother's bathroom has a sewer odor or some kind of bad odor if not used for a few days. She was able to stop it by putting a towel over the bathtub drain when she left the house. I have put a flat rubber stopper over the drain but it isn't stopping it. Now, it appears after someone opens a door in the house. (Possibly pulling the air past the stopper into the house because of air flow?) I have had 2 different plumbers out to the house but they cannot find anything wrong. She had the sewer line replaced several years ago. It may have started happening after that. Would incorrect placement of the sewer line cause this? It does not happen in the other bathroom. She had the house for thirty years and it has only done it in the last few years
Thank you for any help you can give me.
SKW

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 tub 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