We have a second floor room that is centered on top of the house - but this means that the windows of this second story are ABOVE the plumbing vents from the first floor. These plumbing vents are a few feet below the windows and perhaps ten feet away, laterally.

On a regular basis, a sewer gas smell comes into the second floor, presumably from these plumbing vents.

This seems like an easy problem to solve - I see some activated charcoal vent caps that are advertised to solve this very problem. Should be simple.

However, before I just cover over this problem, should I be worried that we're regularly smelling sewer gas from these vents ? Is that indicative of some deeper plumbing problem ? Or is it totally normal for some plumbing installs to just burp sewer gas out the vents during normal, day to day operation ?


  • 2
    If it's not "at least 10 feet away" it's a code violation. In any case it's a violation of common sense not to run them internally to above the topmost roof level of the house unless there's a lot more horizontal clearance, but hey, lazy builders. Code would also be satisfied if they were at least 3 feet above the top of the window. Vents do not "burp sewer gas occasionally" they vent it all the time - you "occasionally notice" when it happens to blow towards the open windows.
    – Ecnerwal
    Commented Aug 13, 2020 at 23:32

1 Answer 1


It is normal for sewage gas to escape from drain vents. That's why they usually vent through the roof, that and unclogging. The vents tie directly into the pipes that lead to the sewers. There are plumbing traps that can cut down on the amount of gas that escapes but some will always escape. The vent cap should help but just make sure they don't seal the vent.

  • I agree if the filter puts two much back pressure on the vent things like toilets not flushing and traps gurgling after finally draining. Will start happening, it is normal for smells to go out the vents.
    – Ed Beal
    Commented Aug 13, 2020 at 22:25
  • if the gas is coming from the public sewer a disconnection trap at the boundary could stop that portion of the gas.
    – Jasen
    Commented Aug 14, 2020 at 7:59

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