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Sewer gas and the porosity of concrete

  1. Mar 19, 2009 #1
    I woke up this morning to find a strong smell of sewer gas in our basement. The smell is gone now. However, I do not know where the exact source is coming from.

    We had this same issue before with one of the pipes in our basement that runs through the floor and connects to the outgoing sewer line. At the time, the flooring around the pipe was cracked quite a bit, so we used concrete (the Quikcrete kind of stuff) to plug the opening.

    I was wondering if it was possible that the concrete is porous enough to permit the sewer gases to pass through it? According to wikipedia, sewer gases can consist of hydrogen sulfide, ammonia, methane, carbon dioxide, sulfur dioxide and nitrogen oxides--real healthy stuff :yuck:.
  2. jcsd
  3. Mar 19, 2009 #2


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    The sewer pipe from your house to the street can be cast iron or concrete or ceramic or plastic. They are all susceptible to root ingrowth at the joints, corrosion from the H2S/H2SO4 and cracking from soil movement so, yes, it could be a leaking pipe. If you have a floor trap or sump down there, it could have dried out as well. You could also have a leak somewhere in the drain waste vent system in the house or even a compressed/deformed wax seal under the toilet causing the problem.

    I wouldn't light a match BTW!
  4. Mar 25, 2009 #3
    Have the problem checked out by a licensed plumber. Remember that "sewer gas" is methane which is odorless and could still be present. The only reason you smelled it in the first place was it was mixed with odors from the sewer. Another common gas in sewers is Hydrogen Sulfide which is an olfactory depressant that means it deadens the sense of smell. After a while you don't smell it and you think the gas went away it didn't your sense of smell did.

    Additionally if the mixture of gas in air is the right concentration, in the flammable range, you won't need to light a match, you could get all the spark you need to ignite it by flipping on a light switch.
    Last edited by a moderator: Mar 25, 2009
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