Main Stack as vent for tub and shower drain

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by mule169, Mar 8, 2017.

  1. mule169

    mule169 New Member

    Joined:
    Mar 8, 2017
    Location:
    Portland, Oregon
    Been lurking here for awhile,

    I'm going through a remodel and I had a question. May seem basic to most, but just wanting to validate my assumptions. I have both a shower and a tub drain that are located very close to my main 4" stack (within 2 feet).

    I'm wondering if I can connect the drains for both into the main stack without an extra vent line. I.E. Can the main stack act as the vent for these two drains.

    They are the top 2 most fixtures in the stack, and no other drains will ever be tyed in above them. If I connected them in this fashion one would technically be "wet vented" as they would be connected one above the other?:
    IMG_20170308_132258.jpg

    I was also thinking of using like a 4x4x2x2 double wye to eliminate the "wet venting" concern:
    6263179-200px.jpg

    Thanks for any feedback in advance.

    Cheers,

    Andy
     
  2. Stuff

    Stuff Well-Known Member

    Joined:
    Mar 7, 2013
    Location:
    Pennsylvania
    If there is nothing above then it is a true vent. Make sure nothing below is relying on this as a vent. You can not use a wye but need a san-tee so as not to siphon your traps. Yes, one over the other is an acceptable wet vent.
     
    Last edited: Mar 8, 2017
  3. Sponsor

    Sponsor Paid Advertisement

     
  4. Smooky

    Smooky In the Trades

    Joined:
    Apr 4, 2011
    Location:
    North Carolina
    Is it being used as a vent for any fixtures below?
     
  5. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    That is the concern. You can't dump your tub and shower into a vent that serves a floor below.
    You will need to bring the tub and shower down and wye in below the downstairs fixtures.

    [​IMG]
     
  6. mule169

    mule169 New Member

    Joined:
    Mar 8, 2017
    Location:
    Portland, Oregon
    Terry, Stuff,

    Thanks for the responses. The floor below is an unfinished basement with no fixtures using the main stack as a vent. I'll install a clothes washer drain in the basement, and I'll ultimately refinish and put a bathroom in the basement, but any fixtures downstairs will have separate vents that will tye into the main stack up in the attic that I'll run through the walls.

    The reason I'm asking about this configuration is really just because of cramped space with tub/shower drains being so close to the main stack, and hoping I didn't have to figure out how to cram in dedicated vent pipes for each drain right before they tye into the main stack.

    Completely understood that no downstream fixtures could use the main stack as a vent in this config.

    I'm fortunate in that, there are 2 other spots in the basement that tye into the main drain/sewer. The kitchen has it's own tye in for a drain (and dedicated vent) as well as one drain entry/cleanout right before the main drain pipe exits the house.

    Stuff, thanks for the reminder about san-tee vs wye. It's like remembering port/left, starboard/right for the newb sailor :) I'll make sure to triple check my work before I install.

    Cheers,

    Andy
     
  7. Stuff

    Stuff Well-Known Member

    Joined:
    Mar 7, 2013
    Location:
    Pennsylvania
    Very strange that a 4" stack has nothing connected to it. No toilets in the house?
     
  8. mule169

    mule169 New Member

    Joined:
    Mar 8, 2017
    Location:
    Portland, Oregon
    Hey Stuff,

    So there is stuff that will drain into the stack, but none of those fixtures will be using the main stack as their primary vent. 30 second diagram from top view of bathroom and side view of basement under bathroom here:
    IMG_20170309_090846.jpg
    IMG_20170309_091111.jpg
    Before the remodel the toilet was over where the tub/shower will be so the toilet did tye directly into the main stack. As it stands now, I'll be venting the toilet, and vanity sink up through the wall and tying them back into the main stack up in the attic.

    -Andy
     
  9. Stuff

    Stuff Well-Known Member

    Joined:
    Mar 7, 2013
    Location:
    Pennsylvania
    Pictures explain things better. You will need some space in the basement to tie all this together.

    Look at Terry's picture of the toilet being wet vented by sink. You usually need to do that to prevent having a horizontal dry vent for the toilet.
     
Similar Threads: Main Stack
Forum Title Date
Plumbing Forum, Professional & DIY Advice Do main stacks have to be vertical? Oct 20, 2020
Plumbing Forum, Professional & DIY Advice Washing machine standpipe, main stack Jul 13, 2020
Plumbing Forum, Professional & DIY Advice Vent basement floor drain into main stack Jun 8, 2020
Plumbing Forum, Professional & DIY Advice Cast drain: horizontal to vertical (main stack) May 7, 2020
Plumbing Forum, Professional & DIY Advice Can you use the main stack to vent? P Apr 11, 2020

Share This Page