Sewer gas smell in the basement?
January 29, 2005 7:13 AM   Subscribe

SewerGasFilter. Help![+]

This morning I detected the stink of sewer gas in my basement for the first time. My plumbing is clean, hasn't ever been worked on (at least in five yrs since I have lived here). Anybody, advice? I've looked for a cheap gas detector but Google-fu fails. I don't want to call the FD or a plumber if this is a transient problem. I'm in NJ where there's been some cold weather. Thanks in advance.
posted by nj_subgenius to Home & Garden (8 answers total)
quick question: does your sewer pipe vent out of your roof? You may want to check and make sure the vent [which in my house just looks like a PVC pipe with a little cap on it coming out of my roof above my bathroom] isn't clogged with snow and/or ice which could make the gasses sneak out little cracks and/or collect in the basement. Also, do you have any plumbing fixtures or drains in your basment that you don't use much? If so, make sure there's still water in the traps that keep the gas from getting in to your house. While I wouldn't freak out about this, sewer gas can be bad for you or potentially flammable in high concentrations, so if you aren't able to resolve this yourself, I would recommend calling a plumber.
posted by jessamyn at 7:37 AM on January 29, 2005

Besides a clogged vent, do you have a sink or washing machine that hasn't been used in a long time? Smell is blocked at the trap in the drain (the S-shaped bend in the drain) by water laying in the bottom of the trap and blocking the flow of gas. If the sink is not used, the water can evaporate, letting the gas in.
posted by 445supermag at 9:21 AM on January 29, 2005


Another quick question: you don't have natural gas or LP gas lines running into the house, do you? Most gas companies put an "odorant" into these otherwise odorless fuels, to tip people off when leaks occur. Since these odorants tend to be mercaptans and sulfides, they might smell plenty sewer-y.

If this might apply, call the gas company pronto.
posted by enrevanche at 9:23 AM on January 29, 2005

What 445supermag said. Any drain out of your house, including maybe a basement floor drain, has an S-trap somewhere to hold water and block sewer gas. If the water has evaporated from one, you would smell sewer gas. Just pour some more water in.
posted by LarryC at 10:06 AM on January 29, 2005

Response by poster: Thanks all - I ran water through a basement toilet that hadn't been used for awhile. I checked the roof vent and all looks OK. The smell has lessened considerably. Whew.
There aren't any cheap detectors a la carbon dioxide for this, are there?
posted by nj_subgenius at 1:46 PM on January 29, 2005

There aren't any cheap detectors a la carbon dioxide for this, are there?
Um, I think you used one of the better ones this time.
posted by Kirth Gerson at 7:11 PM on January 29, 2005

If you have a fixture you don't use pour some mineral oil into the trap. It doesn't evaporate, it'll stop water underneath from evaporating, and it won't hurt anything when you flush it down the drain. Even a thin layer in a toilet bowl will stop the evaporation into the room though a small amount will happen on the other side of the trap.

It's not the CO2 that you have to worry about in most cases. Although CO2 displaces oxygen it's the methane which is flammable and especially the hydrogen sulfides which can paralyze your lungs before you can smell it which are the big dangers.
posted by Mitheral at 11:02 PM on January 29, 2005

I'm having this identical problem right now. Please let me know if you ever figured out a good solution. We've checked the vents to the roof and run water into all our traps.

We replaced the wax seal on the toilet and crawled under the house to see if there was anything wrong there (there wasn't, that we could see, at least).
posted by krudiger at 11:57 AM on November 8, 2005

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