Easy Wet Vent question???

Discussion in 'IPC Plumbing Code Questions' started by walt, Nov 2, 2020.

  1. walt

    walt New Member

    Joined:
    Oct 31, 2008
    Hi all,
    I'm building a small 140 sq ft detached guest room and have what I hope are a couple easy questions about wet vent for its bathroom group. I found lots of diagrams, but none quite identical to what I'm planning. (see attachment). Long narrow bathroom with shower at one end and WC on the other.
    I'm planning to wet vent from the lav in the middle (2"), wye into the shower trap arm (2") and then run another 36" into a san tee in the vertical drain directly under the WC (3"). WC drops straight into the short vertical and then on to join the septic.
    Questions:
    1- The attachment shows shower trap arm dropping down into the wet vent with a rolled wye. But that wye needs to be flat, right?
    2- I'm not sure I can get the 3x3x2 tee up high enough under the WC to run the wet vent drain straight into it. After the wye, can I make a vertical drop in the 2" with two 45's and enter the tee horizontally?
    Thanks in advance. This forum is an amazing resource!
    Walt
     

    Attached Files:

    Last edited: Nov 2, 2020
  2. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    1) Wye flat is best for wet venting.

    2) Can't you just lower all the horizontal drains upstream of that san-tee under the toilet to avoid the need for a vertical offset?

    I think most will say you can't offset a horizontal wet vent with 45s, because you'd be introducing a vertical section. I would say you could offset it with 22.5s, as that's still horizontal, although I may be in the minority. Or better, just use a greater than normal slope on that 36" segment, e.g. 1/2" or 1" per foot. That would be hard to argue with.

    Cheers, Wayne
     
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  4. walt

    walt New Member

    Joined:
    Oct 31, 2008
    Thanks Wayne,
    2- No. There's a beam in the way just before the wye. Angling that last section a bit more than normal might work. Or using 22.5s.
     
  5. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    So how much drop do you need in the 36" between the wye and the san-tee? If this is all in a single joist bay, I would think you could get the san-tee very high up, just below the closet flange if necessary.

    Cheers, Wayne
     
  6. walt

    walt New Member

    Joined:
    Oct 31, 2008
    Right, this is in the same joist bay. The lav will need to come through an adjacent joist to get into that bay, and I was afraid I wouldn't have much space overhead if I bore the joist. But being right by the beam, I suppose I could let the drain rest on the beam and then notch the bottom of the joist. That would allow me to drop the wye several inches.
    So, I think the tee will have room to come up, or the wye will be able to come down enough to make the connection.
    Thanks!
     
  7. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    Best to avoid notching if you can, notching allowances are more limited as they weaken the joists more. For a solid sawn joist of height D, a hole of diameter at most D/3 that is at least 2" clear from the top and bottom and from any other holes is best.

    Cheers, Wayne
     
    walt likes this.
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