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Thread: Vent size ?

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  1. #1

    Default Vent size ?

    I met a plumber I think I want to use but wanted to ask a question about something he said. He was telling me about wet and dry vents which I found interesting and he also told me about some codes in certain areas require a wet vent for each fixture. Well a long story short he told me that if he was to do the job that if I didnr have a problem with it that he would rather use two 2" vents rather than one 4" and that way I can have a 2x4 wall rather than a 2x6 wall and I would have two wet vents for each bathroom rather than one 4" and all the 2" pipes would all come together in the attic and exit through the roof with either a single 3" or 4"
    Does this sound alright ? Advantages/disadvantages ? Thoughts please.

  2. #2
    Plumbing Designer FloridaOrange's Avatar
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    It's done all the time.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  3. #3
    DIY Senior Member seaofnames's Avatar
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    The smaller your venting pipe the better. No need to make the roof vent over 3"

  4. #4

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    Sounds great. Thats another score for this plumber that I believe I want to use for the job.
    Thanks

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Default wet vents

    Think about this. A wet vent means that there is another fixture connected above it to create the wet vent. If EVERY fixture needed a wet vent, how would the upper fixtures get wet vented? The number of vents, and their sizes, is determined by the arrangement of the fixtures. In most areas, and codes, the TOTAL area of the vents through the roof has to equal the area of the incoming sewer to the house. That means that a 4" sewer would require FOUR 2" vents, not two, and a 3" sewer would require the equivalent of two 2" and one 1 1/2".

    Helpful Plumbing Hints for Residential Construction by Bert Polk Plumbing Inspector Lincoln County
    Last edited by Terry; 05-24-2010 at 03:31 PM.

  6. #6

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    Thanks for explaining that hj. I believe he said the same thing but now I better understand it because I can read it again since you typed it. If Im not mistaken he said he was going to leave each bathroom with two 2" vents and there would also be more for the utility room and that they would all come together and exit the roof in a single 4". Well from what information Im getting from here and in combination with what he is telling me then it sounds like he is going to do it right and Im just wanting to make sure.

  7. #7
    Plumber Winslow's Avatar
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    Quote Originally Posted by seaofnames View Post
    The smaller your venting pipe the better. No need to make the roof vent over 3"
    As long as the cross section area through the roof is is equal to or greater than the cross section area of the main drain.

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