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-   -   Minimum vent size for flush valve water closets (https://www.askmehelpdesk.com/showthread.php?t=344853)

  • Apr 22, 2009, 02:39 PM
    RodButler
    Minimum vent size for flush valve water closets
    I think the code says that you need to size a vent at one half the diameter of the largest waste pipe. But I seem to recall somewhere that said a minimum vent through the roof was 3 inches.
  • Apr 22, 2009, 03:12 PM
    massplumber2008
    Hi Rod...

    All houses must, at a minimum, have one 3" vent that penetrates the roof. The minimum vent through a roof, however, is 2".

    The minimum vent required for all water closets, whether 3" or 4" pipe is 2"... so here, the 1/2 diameter rule doesn't apply.

    Let me know if you have more questions...

    MARK
  • Apr 22, 2009, 03:28 PM
    RodButler
    Quote:

    Originally Posted by massplumber2008 View Post
    Hi Rod...

    All houses must, at a minimum, have one 3" vent that penetrates the roof. The minimum vent through a roof, however, is 2".

    The minimum vent required for all water closets, whether 3" or 4" pipe is 2"...so here, the 1/2 diameter rule doesn't apply.

    Let me know if you have more questions...

    MARK

    What about commercial installation using flush valve water closets? Same rule?
  • Apr 22, 2009, 03:31 PM
    massplumber2008
    Same rule... 2" vent required for all toilets!
  • Apr 22, 2009, 04:08 PM
    RodButler

    Awesome, thanks.
  • Apr 22, 2009, 09:34 PM
    Milo Dolezal

    They may be combined... and what you see is 3" or 4" vent end piece that penetrates roof. This is more likely in warehouse-type installations where you have several toilets next to each other...
  • Apr 23, 2009, 04:53 AM
    speedball1
    Quote:

    Originally Posted by RodButler View Post
    I think the code says that you need to size a vent at one half the diameter of the largest waste pipe. But I seem to recall somewhere that said a minimum vent thru the roof was 3 inches.

    My Code requires one thre inch vent per dwelling, (we put ours in the kitchen) and a 2" vent for every fixture that has a trap with the exception of floor drains.Regards, Tom
  • Feb 3, 2011, 04:26 PM
    PlumbRob7
    Hi
    In British Columbia every building must have one 3" vent.. also any water closet must have min. 1.5" vent and 2" wet vent...and floor drains 3" and larger can vent themselves.

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