I recently started installing new floor in our bathroom. I of course took out the sink and toilet, which were left unconnected for about a day and a half (will not do that again). The sink and toilet have both been reconnected for 2 days now, no odors from them, but the floor vent ONLY in that bathroom is emitting a sewage odor. I am on a septic tank. Does anyone know what the potential issue is and a remedy for it? And if I would need to call a plumber or HVAC for this issue if I can't resolve it myself?

I have had zero smells like this before starting work in the bathroom.

  • I assume you're using it for heating at the moment?
    – rogerdpack
    Feb 12, 2022 at 0:28

2 Answers 2


Upon removing the sink and toilet did you accidently splash wastewater into that vent?

It's possible that the sewage smell made it into your return ducts for too long when you left things unconnected for about a day and a half. The smell might have infused itself into your furnace air filter. Try smelling and replacing your furnace filter.

  • Maybe it's a "return duct", but with "the floor vent" maybe OP means the hot air exhaust. Either way, good answer. Cleaning the accessible insides would help too, but if fluids ran down the pipe this is going to be a more difficult problem. (I never understood floor vents in bathrooms... like carpet in bathrooms...)
    – P2000
    Jan 19, 2022 at 17:16
  • @P2000 OP certainly leaves a lot to the imagination. As for "I never understood floor vents in bathrooms"; take your pick: people enjoy a room temperature toilet seat without having it pre-heated by another human, a floor vent is the path of least resistance and the builder doesn't care. =)
    – MonkeyZeus
    Jan 19, 2022 at 17:24
  • Yes, strange how the source of the heat creates such opposite perceptions...
    – P2000
    Jan 19, 2022 at 19:35

You need to dump a small bucket of water in it and it will quit smelling for a while. That drain has a trap that needs water in it to function. No water bad smell. Fresh water no smell.

  • 1
    The OP is referring to an HVAC vent, not the toilet flange.
    – brhans
    Jan 19, 2022 at 1:14

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