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  1. #1
    Join Date
    Dec 2012
    Posts
    1

    Default exhaust fan vent options

    I installed a 100cfm fan in my main bath. I really do not want to vent through the roof. However, there are two sewer vents within five feet of the fan output. These sewer vents have 3" pvc which I could easily tee into. I would then put a rain cap on the vent so it would not ingest water down the bath fan vent ducting. Is there any reason I can't do this? My other option is a sidewall exhaust which would require a 28 foot run. I have a large attic above so space is not an issue.

  2. #2
    Join Date
    Aug 2007
    Posts
    6,617

    Default Re: exhaust fan vent options

    Never, never, NEVER connect anything into the sewer system that is not sewer related!

    Sewer vents are full of toxic, flammable, and malodorous gases, which you do not want coming into the house. Your best option is to either penetrate the roof with the bathroom vent or to exit through a gable end.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  3. #3
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,419

    Default Re: exhaust fan vent options

    Quote Originally Posted by A. Spruce View Post
    Never, never, NEVER connect anything into the sewer system that is not sewer related!

    Sewer vents are full of toxic, flammable, and malodorous gases, which you do not want coming into the house. Your best option is to either penetrate the roof with the bathroom vent or to exit through a gable end.
    Let me add to this excellent advice. If you tap into the sewer vent, then when the fan is not running, those sewer gasses will come into your house and not go up the vent. Many of these gasses, particularly the most toxic ones hydrogen sulfide are heavier than air and are only going up the vent pipe because of gas pressure in the sewer system. They will gladly settle in your bathroom, and they don't smell very good either.

  4. #4
    Join Date
    Sep 2012
    Location
    Boston
    Posts
    888

    Default Re: exhaust fan vent options

    Amen to those two answers.

    it's easier to vent through the roof than through the siding.....or at least as easy... unless you have ceramic roof tiles.

  5. #5
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,438

    Default Re: exhaust fan vent options

    We've discussed this before. I believe that code doesn't allow doing so, no matter where you live.

    Like mentioned above, it's relatively easy to install a new vent through the roof. It can be done in tile roofs as well.

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