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  1. #1
    Join Date
    Mar 2011
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    6

    Default Shower Moisture Venting Question

    Hello, I have a newly installed Shower Vent/fan that just currently just exhausts the moisture into my attic.

    My Question is, can I link the SHower Vent to an Existing VERTICAL Vent Stack? I'm imagining just cutting the Vent Stack and put in a WYE ABS fitting, connect the Shower to the WYE fitting, and the air/moisture goes out the stack.

    Is this to code/legal? Will it work?

    The reason I don't want to go Horizontal and put in a new vent tube out of a wall is because I don't have a hammer drill and bit to punch a 3" or 4" hole in my exterior wall.

    Do I just bite the bullet and go Horizontal?

    In my mind it seems easier to go Vertical using a Vent Stack.

    Thoughts?

    Thanks guys!

  2. #2
    Join Date
    Aug 2007
    Posts
    6,481

    Default Re: Shower Moisture Venting Question

    DO NOT tie your exhaust vent into any plumbing vents in the attic! Those vents are full of sewer gas that is both noxious and toxic.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  3. #3
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,360

    Default Re: Shower Moisture Venting Question

    As said, the gasses are also flammable. Under the right conditions they can explode as the fan motor will easily provide the needed spark to ignite the gas.

    Use a separate vent. If you have a typical composition shingled roof its fairly simple to cut a hole, and use a roof jack to cover the vent pipe. We prefer type B vent caps to keep the rain out.

  4. #4
    Join Date
    Mar 2011
    Posts
    6

    Default Re: Shower Moisture Venting Question

    Thanks so much for the suggestions guys!

    I totally forgot about the gases (explosive) inside those pipes.

    Looks like maybe I can rent a hammer drill and drill a hole in the exterior wall for a side vent cap.

    I have clay roof tiles so I don't even want to bother with that stuff.

    thanks again for the suggestions!

  5. #5
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,081

    Default Re: Shower Moisture Venting Question

    I see a possible problem going horizontally. You need to check your local code about that, down at your building department.

    In my city there is a formula that allows only a portion of the vent to go horizontally.

    BTW, there are many old homes around, which have fans venting into attics. But new constructions needs to be to current code.

  6. #6
    Join Date
    Jan 2009
    Posts
    14

    Default Re: Shower Moisture Venting Question

    I moved into an older house in the country a year ago and found out that mine vented into the attic. I didn't like the idea of going through the roof, so I went out the gable side of the house. I didn't have a hole saw for the 4 inch attachment to my drill so I found a whole set through harbor freight for a real reasonable price. Installation was a breeze, just check to see if you need a converter for the fan box to go from a square to round opening to connect the hose. Much better than having moisture in the attic!

  7. #7
    Join Date
    Mar 2011
    Posts
    6

    Default Re: Shower Moisture Venting Question

    snyder...: I agree about not having moisture in the attic. I don't want to attract termites by having moist wood in my attic.

    dj : Yes i agree, I will have to check with my local building codes before I proceed.

    I think from my fan to the closest wall, it's about 10-12ft. I figure if I do 1/2inch slope upwards every 4 feet, I should be ok.

  8. #8
    Join Date
    Aug 2007
    Posts
    6,481

    Default Re: Shower Moisture Venting Question

    Quote Originally Posted by dawaves View Post
    I think from my fan to the closest wall, it's about 10-12ft. I figure if I do 1/2inch slope upwards every 4 feet, I should be ok.
    Actually, you want it to slope the other way, away from the fan, so that moisture runs out towards the exit, not back into the fan.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  9. #9
    Join Date
    Mar 2010
    Location
    Canada
    Posts
    86

    Default Re: Shower Moisture Venting Question

    Quote Originally Posted by dawaves View Post
    Hello, I have a newly installed Shower Vent/fan that just currently just exhausts the moisture into my attic.

    My Question is, can I link the SHower Vent to an Existing VERTICAL Vent Stack? I'm imagining just cutting the Vent Stack and put in a WYE ABS fitting, connect the Shower to the WYE fitting, and the air/moisture goes out the stack.

    Is this to code/legal? Will it work?

    The reason I don't want to go Horizontal and put in a new vent tube out of a wall is because I don't have a hammer drill and bit to punch a 3" or 4" hole in my exterior wall.

    Do I just bite the bullet and go Horizontal?

    In my mind it seems easier to go Vertical using a Vent Stack.

    Thoughts?

    Thanks guys!
    As others have said, NEVER do this.

    More importantly and to answer your question(s) ..
    Is this to code/legal? Will it work?
    No, it's not allowed by code therefore it's not legal. It would sort of work but will also cause major problems with the drains.

    Aside from sewer gases backdrafting into the fan you would be putting the vent stack into negative pressure when the fan was on.
    Contrary to popular belief the primary function for the vent stack is not for exhausing sewer gas but to provide air admittance for the gravity drain system within homes. When water is flowing down the drain lines this creates a draw from the vent stack to provide air behind water in order for the water to gravity drain with good velocity.
    If you connected the bath exhaust fan to the vent stack , once you turned on the fan this would prevent the drain lines from functioning properly while the fan was exhausting.

    Quote Originally Posted by dj1 View Post
    I see a possible problem going horizontally. You need to check your local code about that, down at your building department.

    In my city there is a formula that allows only a portion of the vent to go horizontally.

    BTW, there are many old homes around, which have fans venting into attics. But new constructions needs to be to current code.
    Perhaps that may be a consideration in your municipality but I don't anticipate a horizontal exhaust being a code issue anywhere else. Besides I'm not sure why it would be , aside from exhausting out the soffit ( which it never should be ).
    It's rare in our area to put the exhaust through the roof with pretty much all being exhausted horizontally through a wall at some point.

    Wheter it's an old house or new construction the bath exhaust is never allowed to dump into an attic in most jurisdictions I'm aware of. It's simply not a good idea when you consider the amount of mould and structural damage caused by the excessive moisture being dumped in the attic.

    Quote Originally Posted by A. Spruce View Post
    Actually, you want it to slope the other way, away from the fan, so that moisture runs out towards the exit, not back into the fan.
    I totally agree, this is the proper method.

  10. #10
    Join Date
    Mar 2011
    Posts
    6

    Default Re: Shower Moisture Venting Question

    Leonard: Thank you so much for the info! Yes I agree with you 100%

    Followup Question: Regarding the slope of the vent out to the side wall.

    If the slope should be going downward, do I go 90 degree up and then do a 45 degree angled down toward the side wall? I ask this because I think my vent fan has an exhaust on the side. So I imagine I'll put a 90 degree vent pipe pointing upward, go up about 2 - 4 feet and then put a 45 degree out to my wall vent.

    Does this sound about right?

    If I do this, won't the moisture going up the pipe the 2-4 ft run back down?

    thanks guys!

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