Venting question

Discussion in 'UPC Plumbing Code Questions' started by tomski, May 1, 2021 at 8:02 PM.

  1. tomski

    tomski New Member

    Joined:
    Feb 13, 2021
    Location:
    auburn, CA United States
    I've attached a layout of my proposed plumbing for an addition. I'm in California so UPC.

    I've read that a 2" vent can take care of 24 DFU's. I have a total of 8 DFU's so I thought I could combine the two 2" vents in the attic to one 2" vent through the roof.

    However, I've also read that the area of all the vents must be greater than the area of the main drain. My main drain is 3" so by this standard I need 7.07 sq. inches. Even if I use a 2" vent through the roof for the kitchen sink and another 2" vent through the roof for my bathroom group I am still short of the 7.07 sq. inches. Am I missing something or do I have to add another vent pipe somewhere? Thanks for your input.
     

    Attached Files:

  2. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    Through the roof, two 2" vents and a 1.5" vent.
    The kitchen sink is getting the 1.5" vent, and the bathroom group is the 2".
    You have other plumbing in the home, right?
     
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  4. tomski

    tomski New Member

    Joined:
    Feb 13, 2021
    Location:
    auburn, CA United States
    Yes there is other plumbing and vents in the main part of the house.....forgot about those so that would take care of the total vent area.

    Just to clarify, you said 2 2" vents and one 1.5" vent. I assume you meant one 2" and one 1.5"?
     
  5. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    Under the UPC, if you have 3 WCs or less, the minimum size building drain is 3". With 4 WCs, the minimum size building drain is 4". The total vent area through the roof has to be at least the minimum size building drain.

    For 3" minimum area, you could obviously do a 3" vent. Or you could try (2) 2" vents, but 2^2 + 2^2 = 8 < 9 = 3^2. So that's not quite enough, you'd need to use (2) 2" vents and (1) 1.5" vent, which was Terry's point.

    For 4" minimum area, you could do a 4" vent, (2) 3" vents, (1) 3" vent plus (2) 2" vents, (4) 2" vents, (3) 2" vents and (2) 1.5" vents, etc.

    Cheers, Wayne
     
  6. tomski

    tomski New Member

    Joined:
    Feb 13, 2021
    Location:
    auburn, CA United States
    Ahhh. I'm so focused on the new plumbing, I keep having tunnel vision. I wasn't realizing Terry was talking about the house in total, not just the new addition. Sorry, I'm usually not so dense. Thanks again to both of you for the help.
     
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