Two designs of a new washroom for review

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by Buttonsrtoys, Dec 16, 2012.

  1. Buttonsrtoys

    Buttonsrtoys New Member

    Messages:
    22
    Location:
    Nova Scotia, Canada
    I'm adding a half-bath to on the first floor and tying into an existing sanitary line for the full bath above. Below are two designs. Design "A" runs the vent for the half-bath above the flood level of the fixtures in the full bath. Design "B" is a bit simpler on paper, but the existing riser is in an exterior wall next to a post at the point of the tie-in, so its a bit trickier to build than design "A". The sketches don't show the jogs in plan-view, which some lengths I relate may look out of scale.

    I annotated the sketches with ABS pipe sizes and lengths. Blue lines are the existing sanitary, green is the new.

    Are both of these designs OK? Code-wise, I'm in Nova Scotia.

    WashroomA.jpg
    WashroomB.jpg
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,508
    Location:
    Cave Creek, Arizona
    Desigh "A" is the only one that will work and that assumes you actually install it the way it is drawn. "B" would not pass any code that I am aware of.
  3. Buttonsrtoys

    Buttonsrtoys New Member

    Messages:
    22
    Location:
    Nova Scotia, Canada
    Thanks hj. I'll install "A" as drawn. What's wrong with "B"?
  4. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,244
    Location:
    Land of Cheese
    "B" is not acceptable because once the line has been used for a drain, it can no longer be used as a vent. The only exception is the wet vent of the water closet past the lavatory.
  5. kreemoweet

    kreemoweet New Member

    Messages:
    371
    Location:
    Seattle. WA
    "B" is the old "single stack" plumbing system design, as far as I know it was outlawed in the early part of the last century.
    Also, in "A", I think you need to keep the toilet/lav vent size at 2 inches all the way up, rather than reducing down to 1 1/2
    inch as shown.
  6. Terry

    Terry Administrator Staff Member

    Messages:
    14,904
    Location:
    Bothell, Washington
    A

    And like mentioned above, keep the lav, including the vent, 2" all the way up to the next floor on the revent.
    You can use the 1.5" traparm for the p-trap on the lav.

    Below is an example of wet venting

    [​IMG]
    Last edited: Dec 16, 2012
  7. Buttonsrtoys

    Buttonsrtoys New Member

    Messages:
    22
    Location:
    Nova Scotia, Canada
    Thanks guys. "A" it is with a 2" vent. Wet venting makes my head spin...
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,508
    Location:
    Cave Creek, Arizona
    quote; Wet venting makes my head spin

    Wet venting is simple, but your ""B" is an illegal "wet vent" because you cannot wet vent between floors.
  9. Buttonsrtoys

    Buttonsrtoys New Member

    Messages:
    22
    Location:
    Nova Scotia, Canada
    Ah. That clarifies what was confusing me. So wet vents are OK provided their short/restricted to the same floor. Thanks! Now I'm curious - why are long wet vents between floors a problem?
  10. Terry

    Terry Administrator Staff Member

    Messages:
    14,904
    Location:
    Bothell, Washington
    The same reason that standpipes can only be so long. They siphon traps.
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