Sewer smell in only one bathroom

[Andrea D]

We moved into an older home (built 1974) a little over a month ago. We had an extremely thorough inspection prior to settlement. The previous owners had updated a few of the bathrooms in 2018. They were not at the home often, so when we arrived, there was a smell in the main kitchen sink when you ran hot water. Turns out the water heater was set at a low temp. Raising it fixed that issue. A couple of weeks later, we started smelling a cabbage/sewer smell coming from one of the upstairs bathrooms. There are three upstairs and this is the only one that smells. Sometimes, when taking a shower in one of the other two, the smell gets worse. This was one of the updated bathrooms, so the toilet is new and installed last year. There’s no exhaust fan in this bathroom, so we can’t really ventilate it out, either. I tried pouring down a diluted bleach solution in the drains but that didn’t help. We have a septic (but public water), and it does smell like the faint odor that wafts from the septic tank outside. However, that was inspected and pumped prior to us moving in. We had a plumber come out recently and he gave us two options-pull up the toilet tank and check to see if it’s the wax seal or perform a peppermint test. Which would be the best to do first? The estimates were around the same for each. Suggestions on this or if there are any other ideas for the reason for the smell would be appreciated!!

 

[Reach4]

However, that was inspected and pumped prior to us moving in. We had a plumber come out recently and he gave us two options-pull up the toilet tank and check to see if it’s the wax seal or perform a peppermint test.

Make sure all drain traps have water. Floor drains. Sink drains.
You can cover the suspect toilet or other fixtures with cheap plastic dropcloths. If you lift the one coverings the next day, and smell the smell, you know where to concentrate. If the smell comes from the toilet, yes the wax ring would be the first thing.

I would sanitize my well and plumbing. https://terrylove.com/forums/index.php?threads/well-sanitizing-extra-attention-to-4-inch-casing.65845/ is my writeup for deep wells that are bottom feeding. It may be overkill, but overkill is appropriate IMO.