Sewer gas smell in bathroom is a mystery?

[Mjchevalier]

I own a 2 story townhome on a slab with no basement. Our downstairs bathroom has had a sewer smell develop in it and I also noticed the toilet was rocking side to side. I pulled it off to find a broken pvc closet flange. Replaced the flange and set it back on with a new thick wax ring with no horn and it felt like a very secure seal. The next day I started smelling a similar sewer gas smell but the toilet is sealed nicely and solid as a rock. Crawled around the floor and smelled the toilet and sink drain but cannot isolate the source of the smell. There is just a toilet, sink vanity and exhaust fan in the ceiling of this bathroom. I am lost at this point and don’t understand where this sewer smell is coming from. Looking for help. Thanks

 

[Dj2]

If the smell comes from the toilet drain, you may have an incomplete seal at the wax ring/bowl.
Is the new flange lower than the finished floor? If yes, double the wax rings or use sani-seal.

 

[Sponsor]

 

[Reach4]

Crawled around the floor and smelled the toilet and sink drain but cannot isolate the source of the smell.

A cheap plastic drop cloth can isolate smells for purposes of testing. https://www.walmart.com/ip/Husky-Plastic-Drop-Cloth-0-7-Mil-3-Pack/17217856

 

[Mjchevalier]

A cheap plastic drop cloth can isolate smells for purposes of testing. https://www.walmart.com/ip/Husky-Plastic-Drop-Cloth-0-7-Mil-3-Pack/17217856

So I tried the smart plastic drop cloth idea to see if the sewer gas smell is coming from the toilet but it is not. My wife who has a keener sense of smell than I got down on the floor and swore that the smell was coming from the baseboard. I pulled off a piece of baseboard next to and behind the toilet and it STUNK. This had Me completely baffled. But now a couple of days later the smell is still there but all the baseboard was removed two days ago. So the smell is coming from somewhere behind the wall?? I am completely lost trying to find the source of this smell. It is definitely a sewer gas smell. But how could it be coming from behind the wall? The utility room is behind the bathroom with a furnace and hot water heater. I checked the utility room for odors but nothing smells in there at all. This is bizarre. I don’t know what to do. Please help.

 

[Terry]

Sometimes you can paint over the smell, if in fact what you are painting over is the source. Zerolac or other lacquers meant to seal can work.
I once had a bathroom I was working on where the rodents had been in the wall and were using it for a toilet.

 

[Reach4]

. So the smell is coming from somewhere behind the wall?? I am completely lost trying to find the source of this smell. It is definitely a sewer gas smell. But how could it be coming from behind the wall?

There are some tests for sewer gas leaks. One is a smoke test where smoke is introduced. Another is a peppermint oil test where the peppermint oil is dropped down a roof vent, and one or more people sniff around for the smell of peppermint inside. You can search for such info. I think the smoke test would use special equipment, but the peppermint test can be DIY I think.

The person who drops the peppermint oil cannot be one of the sniffers, because his smell will be overwhelmed by the peppermint oil that he poured.

 

[Highlander]

Sometimes a longer than needed nail or screw (maybe for the baseboard, mirror, cabinet etc...) hits the drain or vent pipe in the wall and over time lets the smell out. Someone else posted something similar today or yesterday.

 

[Mjchevalier]

Hi guys, thanks Reach, Terry and Highlander for the great posts and help. I couldn’t take the suspense any longer and it was driving me crazy where that nasty smell was coming from. I laid on the floor and smelled all around the walls of the bathroom where the drywall meets the floor after all the baseboard had been removed. There was one area where the smell was particularly strong so I got out my drywall poke saw and cut about 4” out horizontally across and about 3” up from the floor and there it was, a dead decaying and rotting mouse that stunk to high heaven. That was it. No sewer gas leak just a dead mouse about 2 feet from my toilet. A plastic bag and some Clorox bleach and now the smell is history.
Thank you so much for all the great troubleshooting. And thank you Terry for this fantastic forum. Much appreciated. Marc

 

[Dj2]

It looks so innocent...

Dead mouse/rat odor is distinctively different than sewer smell.
You should have told us that you smelled a rat from the beginning...