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Thread: Vent pipe size thru roof

  1. #1
    DIY Member George R's Avatar
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    Default Vent pipe size thru roof

    Adding a new 1/2 bath, just a sink and a toilet. The vent for the sink (1 1/2") and the vent for the toilet (2") will join together in the attic and then exit the roof. These vents are not tied in to any other vents in the house. Can this vent exit the roof as 2" or does it need to be increased to 3" before protruding. No inspection in this town, however, I do want to do it correctly.

  2. #2
    Master Plumber Dunbar Plumbing's Avatar
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    Default

    In Ky, the vent has to increase to 3" 18" before it penetrates the roof and must protrude the roof a minimum of 12".

    The pipe need to extend higher than 12" if the pitch of the roof is steep in my opinion.


    The reason for 3" minimum is to prevent frost-over.
    Read what the end of this sentence means.

  3. #3
    DIY Member George R's Avatar
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    Thumbs up

    Gotcha Rugged, 3" it shall be. Thanks

  4. #4
    Moderator & Master Plumber hj's Avatar
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    Default vent

    Where do you live? If it is a cold area of the country then you have to increase it to minimize the possibility of hoar frost closing it.

  5. #5
    DIY Member George R's Avatar
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    Smile

    Central Illinois. It gets cold here.

    HA! Never heard the term hoar frost before. Looked it up on wikipedia, and learned all kinds of new things. Thanks HJ.
    Last edited by George R; 07-21-2006 at 06:06 PM.

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