Combining Vent Pipes

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by supermattthehero, May 2, 2010.

  1. supermattthehero

    supermattthehero New Member

    Messages:
    78
    Location:
    virginia
    I have four 1-1/2" vent pipes in my attic that I would like to combine into a single exit through the roof. What size should that pipe be, or how should I do it?

    Do the pipe sizes need to increase as they are combined (as with drain pipes)?

    Thanks
  2. shacko

    shacko Master Plumber-Gas Fitter

    Messages:
    561
    Location:
    Rosedale, Md
    You can combine them into one 2in. vent. Do you have a larger vent in that area? if so you can run them into that if it's 3in. or larger.
  3. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    you can join them all together but the size after joining depends on what is attached to the individual vents, depending on which code you are under. According to the UPC you can join them all together under a 2" vent as long as the overall fixture units do not exceed 24.
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