Wet vent without the dry vented fixture

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by ghaun, Mar 12, 2021.

  1. ghaun

    ghaun Member

    Joined:
    Mar 12, 2021
    Location:
    West Chester, PA
    Wayne, thank you.

    So, I thought that once the wet-vent portion of a horizontal wet-vented bath went vertical, it could not go horizontal again. Is that not the case?
     
  2. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    That's a good question. Here's the language from the IPC:

    https://up.codes/viewer/pennsylvania/ipc-2015/chapter/9/vents#912.1

    My reading is that the yellow wet vent I drew meets those requirements, bearing in mind that the definition of "horizontal branch drain" includes the phrase "with or without vertical sections or branches"

    https://up.codes/viewer/pennsylvania/ipc-2015/chapter/2/definitions#horizontal_branch_drain

    If for some reason I'm mistaken or you're concerned I'm mistaken, you could pull another dry vent off the yellow vent at the point where the upstream horizontal segment turns down vertically, as per your earlier drawing.

    Cheers, Wayne
     
  3. ghaun

    ghaun Member

    Joined:
    Mar 12, 2021
    Location:
    West Chester, PA
    Wayne,

    My concern is that when going to a horizontal, I introduce another turbulent flow which can block the vent from the waste. I think that is why it has to go vertical. I think that my original diagram would work, but I am not sure if the code would allow it. The vanity would have a dry vent and the wet vent for the tub would be washed as well.
     
  4. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    My understanding is that the increased size requirements for wet vents vs drains not used for venting takes care of all this. For example, in the IPC, a 1-1/2" wet vent can only carry 1 DFU, while a 1-1/2" regular horizontal branch can carry 3 DFU. Or a 2" wet vent can only carry 4 DFU, while a 2" regular horizontal branch can carry 6 DFU.

    I don't see anything in the referenced code language that would prohibit the horizontal/vertical/horizontal wet vent geometry I posted; if there's an intention to prohibit it, the language fails completely to express that intention.

    If you want to extend the vertical portion of the wet vent upwards as a separate dry vent, that is definitely allowed. Again, there's no language prohibiting it.

    Cheers, Wayne
     
  5. ghaun

    ghaun Member

    Joined:
    Mar 12, 2021
    Location:
    West Chester, PA
    Wayne,

    Thank you. I think that I will likely go with something like this in the attached diagram. Thoughts? Bath-Vanity.jpg
     
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