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  1. #1
    Join Date
    Oct 2009
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    Question Dripping water down vent pipe

    When we remodeled my bathroom, replaced part of the vent pipe with pcv. Ever since I have water drip down, so much I have to catch it with a bucket. Not in the summer though. Rebooted it on the roof, didn't help. Had a friend go in the attic to see if it was running down the pipe from the roof, could not detect any. We are stumped.

  2. #2
    Join Date
    Aug 2007
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    Default Re: Dripping water down vent pipe

    Not in the summer though
    A couple of things come to mind .........

    Is the penetration for the vent pipe into the attic well sealed?
    This might be caused by condensation dripping down the vent stack
    A good method would be use a can of spray foam to ensure a tight air seal around the vent pipe penetration into the attic. This will prevent warm moist air from rushing up the cavity into the cold attic and condensing.

    The other thing would be if the connection for the PVC was made to a cast iron vent stack ...... the coupling connector might be leaking. This could also have condensation dripping back down form the warm air in the pipe condensing when it meets the colder attic.

    Just a thought.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
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    Default Re: Dripping water down vent pipe

    I thought about sealing off the opening but was afraid the water would pool in the cavity and ruin the dry wall or worst mold

  4. #4
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    Dec 2009
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    Default Re: Dripping water down vent pipe

    I am having a similar problem - the stack pipe itself is sweating where it goes through the roof . What a;bout insulating the pipe itself??

  5. #5
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    Default Re: Dripping water down vent pipe

    Sure you can.
    Trying to keep the air inside the pipe warmer will help to prevent condensation.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  6. #6
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    Default Re: Dripping water down vent pipe

    Quote Originally Posted by Tweedy View Post
    I thought about sealing off the opening but was afraid the water would pool in the cavity and ruin the dry wall or worst mold
    There isn't any water in a vent pipe other than rain water. You need to keep the cold attic air from mixing with the warm moist inside air causing condensation in the wall cavity. Seal up the opening to the attic and your problems should clear up. Don't insulate the vent pipe, that will allow the outside air coming down the inside of the pipe to make it colder, not warmer.

  7. #7
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    Default Re: Dripping water down vent pipe

    Quote Originally Posted by keith3267 View Post
    There isn't any water in a vent pipe other than rain water. Seal up the opening to the attic and your problems should clear up. .
    For the most part that's true however , the sewer gas contains lots of moisture. When it's allowed to suddenly cool it will condense on the inside or it may cause the outside of the pipe to condense by warming the surface within a colder attic space.

    You need to keep the cold attic air from mixing with the warm moist inside air causing condensation in the wall cavity.
    Yep --- totally agree.

    Don't insulate the vent pipe, that will allow the outside air coming down the inside of the pipe to make it colder, not warmer
    Actually by insulating the outside of the pipe in the cold attic space is helpful. By keeping the pipe warm prevents the moist air inside the pipe condensing when the surface of the pipe becomes suddenly colder.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  8. #8
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    Nov 2009
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    Cairns
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    Default Re: Dripping water down vent pipe

    roof leak - dripping down vent pipe.

    When it rains there is a minor leak down the 4 inch metal (galvanized tin i guess) vent pipe that feeds down through the roof to the hot water tank. There is a much larger vent pipe for the furnace which is installed in the.

    Anyway, what I can definitely tell you is that water runs down the outside of the 4 inch pipe and then drips when it reaches an elbow below. What gives???? dbteeitup.
    Last edited by Starlyjff; 12-17-2009 at 01:25 AM.

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