minimum drain pipe size for a lav

Discussion in 'Canadian Plumbing Code Questions' started by poky1234, Mar 31, 2013.

  1. poky1234

    poky1234 New Member

    Messages:
    27
    Location:
    Woodbridge Ontario
    Hello, Can someone tell me if an 1 1/4 pipe can be used to drain a lav? The drain pipe would run 4 to 5 feet ,then connect into the vertical 3 inch main waste stack. Also , because of the short distance,would it still require its own vent?

    Thanks
  2. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,244
    Location:
    Land of Cheese
    In the U.S., the trap and trap arm of a lav is commonly 1-1/4", but the drain is run in 1-1/2".

    From the International Plumbing Code (IPC)
    vents.jpg
  3. Terry

    Terry Administrator Staff Member

    Messages:
    14,939
    Location:
    Bothell, Washington
    The lav should have a vent before it enters any "waste" stack.

    A lav can wet vent a shower, tub or toilet, but you can not run down waste on top of it in that manner.
    Last edited: Apr 1, 2013
  4. mikeplummer

    mikeplummer Plumber

    Messages:
    190
    Location:
    Ontario, Canada
    it can be 1-1/4" drain and can be stack vented if there is no discharge upstream of where it connects to the 3" main. If there is discharge from above that connection then it does require tis own separate vent
  5. poky1234

    poky1234 New Member

    Messages:
    27
    Location:
    Woodbridge Ontario
    Thanks for the replies guys. Mikeplumber, that is exactly what we are doing. I just needed to know if 1 1/4 is ok. This is for a custom floating boathouse that has very tight quarters and is a little unconventional. I have another question but I'll post it with a pic and drawing.
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