Plumbing in the Home/sewer smell


We live in a 1972 mobil home and are smelling sewer when flushing the toilet in the masterbath. It is the only drain in the house that causes the smell. We have replaced the wax under toilet but not the problem. The smell comes out the air vents to the front room and in the bedroom. It is the only areas that have the smell. I have been told about a vent on the roof that could be the problem but have never seen or heard of before, so not sure what to look for up there.

Hi Mark,
I'm not quite understanding something. When you say "The smell comes out of the air vents to the front room and in the bedroom.", What vents are you talking about? There really shouldn't be any vents from the sewer system open to the interior of the house.

Any plumbing drain must have or be connected to an atmospheric vent. Most typically, these vents extend out through the roof to the atmosphere.
The primary purpose of the vent is to allow air into the plumbing system so that a vacuum doesn't form when you run water down the drain. It's sort of like when you hold your finger over the end of a straw that's full of liquid, the liquid will not drain out until you remove your finger and provide a vent to atmospheric pressure.

Sometimes, due to physical or atmospheric conditions, the odors from the venting system can make their way back in through open windows. That may be what is happening. The reason that it happened on the toilet is that when you flush the toilet,that's the largest amount of water sit down the drain in one shot. Everything else is usually pretty slow and not in high-volume.

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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


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