wet vent tub and sink - will this work?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by leonk, May 7, 2014.

  1. leonk

    leonk New Member

    Messages:
    10
    Location:
    Ontario
    [​IMG]

    I hope the above explains what I'm trying to do. The drain continues to the stack. Is the above allowed? Is there a "smarter" way of doing this? I'm able to move plumbing and vents around, just not fixture locations (e.g. add a vent for the tub if needed rather than wet vent through lavatory)

    Just in case the above isn't clear, the "black" pipes are horizontal / in the floor, between joists. The "blue" is in the wall / vertical.
  2. leonk

    leonk New Member

    Messages:
    10
    Location:
    Ontario
    [​IMG]

    The above is another possible configuration using 2 vents / no wet venting. Will this work better? Also, is there a minimum distance between weir on tub/shower P-trap and wye for air vent?
  3. Bill Shack

    Bill Shack 30years plumbing 10years plumbing inspector

    Messages:
    39
    Location:
    montreal quebec Canada
    The first one is ok if 1) the shower drain is 2 inches and the distance between the shower p-trape and the vent is less than 8 feet and the slope is less than 2 inches .
    2) The second one is ok if more than 8 feet and more slope than 2 inches
  4. leonk

    leonk New Member

    Messages:
    10
    Location:
    Ontario
    The problem I have is the vent/drain.

    1) vent enters cast iron stack with 1 1/4" galvanized pipe (it was connected to ABS in the 1970's using screw on ABS fitting)
    2) drain size is 1 1/2". It enters stack lower using nohub fitting.
  5. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,237
    Location:
    Land of Cheese
    In the U.S., the wet vented section can be no less than 2" pipe. It is not normally an issue here as our codes require 2" for a shower anyway. Using a smaller pipe would compromise the vent.
    I would cut a new tee into the stack for a 2" drain.
  6. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,060
    Location:
    Maine
    Nope, not necessarily so. The IPC will let you wet vent with 1-1/2"
  7. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,237
    Location:
    Land of Cheese
    On the horizontal Tom?
  8. leonk

    leonk New Member

    Messages:
    10
    Location:
    Ontario
    In Canada Tub and lavatory are allowed to connect on 1 1/2" pipe and vented by 1 1/4" air vent. It seems I might not have a choice by to run 2 vents as per second picture. Is there a limit on how close the vent can be to a P trap? I read somewhere 18" .. is this correct?

    As for cutting stack. No go. It's 100 year old cast iron in EXCELLENT condition.
  9. Sean Beck

    Sean Beck Plumber

    Messages:
    68
    Location:
    Toronto, Ontario, Canada
    Stick with your initial drawing. You are fine with the 1.5" drain for the tub/shower and the 1.5" wet vent. A 1.5" wet vent can take 2 fixture units. A basin sink is only 1 so you are fine.

    Yes there is a limit on the distance the vent has to be from the trap. It has to be a minimum of two times the pipe diameter away (2 x 1.5" = 3"), and a maximum of 6ft away with 1/4" per foot slope.

    plumbing.jpg
  10. leonk

    leonk New Member

    Messages:
    10
    Location:
    Ontario
    Sean, there's so many codes out there, it's overwhelming when you have something like the internet.

    In the table you provided, "Maximum hydraulic load", does that equate to number of fixtures? Some codes (like the uniform plumbing code) use DFU's (drainage fixture unit value). It assigns "1" to lavatory, but "2" to tub. If your table describes something like DFU's, then I will be over the 1 1/2". Also, part of the wet vent is horizontal (about 6") does that make a difference?
  11. Kiton

    Kiton Member

    Messages:
    61
    Location:
    Quebec
    edit:
    Sean beat me to the punch.
  12. Sean Beck

    Sean Beck Plumber

    Messages:
    68
    Location:
    Toronto, Ontario, Canada
    Hydraulic load is the term used for the total combined amount of fixture units (FU's). A bathtub is actually 1.5 fixture units.

    I understand what you are trying to say, but the most downstream fixture (the bathtub in this case) isn't taken into consideration when sizing a wet vent. This means that the only FU draining into the wet vent will be 1 (basin sink).

    The horizontal section isn't the wet vent. That is the fixture drain for the bathtub. The wet vent is the section from the top of the wye on the bath drain to the tee-wye that serves the basin sink.
  13. Sean Beck

    Sean Beck Plumber

    Messages:
    68
    Location:
    Toronto, Ontario, Canada
    Oops sorry!
  14. leonk

    leonk New Member

    Messages:
    10
    Location:
    Ontario
    Right. Got that. Except the wet vent you describe is not 100% vertical. The Wye is between the floor joists. It travels about 6" into a 90 elbow, and then goes up between wall joists. and enters the bottom of the sanitary T. Where the top of the T is clean vent (1 1/4") and the horizontal part of the T goes across joists to the sink using 1 1/2" pipe.

    Given this description, I'm still ok?
  15. Sean Beck

    Sean Beck Plumber

    Messages:
    68
    Location:
    Toronto, Ontario, Canada
    There is no limit on the actual length of the wet vent, and it is allowed to change direction providing you give it sufficient slope. So yes you're still okay.
  16. leonk

    leonk New Member

    Messages:
    10
    Location:
    Ontario
    Thanks for all the input Sean!

    I have a whole new appreciation for plumbers with this bathroom reno.
  17. Sean Beck

    Sean Beck Plumber

    Messages:
    68
    Location:
    Toronto, Ontario, Canada
    No problem, happy to advise.
  18. Kiton

    Kiton Member

    Messages:
    61
    Location:
    Quebec
    100%!

    Not only for knowing how to it right the first time, on time, but overcoming all the obstacles (beams, wiring etc) to get it done.
    2 full kitchen renos, 1 2 inch roof to stack drain line replaced, the upper bathroom done and now prepping for the lower bathroom.
    It ain't as easy at it looks!
    Thank god for some help along the way!
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