Perplexing DWV layout challenge in bathroom remodel

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by rickz, Apr 25, 2015.

  1. rickz

    rickz New Member

    Joined:
    Apr 20, 2015
    Location:
    Toronto, ON
    I’m stumped trying to figure out the best way to vent the new drains in my master bathroom remodel.

    Background:
    8” joists are freshly sistered. New shower, tub and vanity means some plumbing layout changes.

    The tub and shower drain placements are pretty much in the same place as original and drains will parallel the joists to a consolidated drain pipe on one side of the room in a drop box under the joists that eventually heads down.

    The old bathroom had most of the venting laid out horizontal above the floor to the nearest walls. The new layout requires them to be under the floor.

    I’m thinking the best way to vent the shower and tub is to take 1.5” vents off the 2” drains with a wye 2 feet or so after the p-trap, but I’m afraid the trap slope will not give me enough vent rise to the wall since I have to go at least 6 feet with the vent, and 10+ feet in the other direction with the horizontal vent before i can go up.

    1. Is this a suitable option?

    2. Am I better to have a shorter trap to lessen the horizontal vent run?

    3. Does it matter if the initial vent wye isn’t rotated up very much? There’s not much headroom to work with while maintaining correct upward vent slope and downward drain slope.

    4. other comments? (this is my first post here).

    note that in the picture of the new pipes I've not yet cut or included all the pieces...
    drain n vent.jpg shower n tub drain n vent plan.jpg consolidated drain.jpg
     
  2. bluebinky

    bluebinky Member

    Joined:
    Aug 31, 2011
    Occupation:
    Electrical/Embedded Software Engineer, Retired
    Location:
    Des Moines, WA
    Basically, vents must run vertical, not horizontal. You simply cannot vent the way you are proposing.

    What is below all of this? Going lower would be ideal.
     
  3. Sponsor

    Sponsor Paid Advertisement

     
  4. rickz

    rickz New Member

    Joined:
    Apr 20, 2015
    Location:
    Toronto, ON
    You can see in the pre-demo picture how the old shower drain went 4+ feet, had a vent pop up and go over the floor (under the old vanity) to the wall. The tub drain also came up above the floor (it was a boxed in tub) and went up the old shower wall which is now gone.

    In the new arrangement, that's not really a choice. Neither is going through the joists, since they are only 8" and the vent would be below the drain. Also bad.

    The kitchen is below, so no room for a dropped ceiling.

    I could run vent and drain parallel to the joist 2' directly to the outer wall of the shower and vent up and drain down. That appears to be against code and not smart in winter climates in general since it's only brick, sheathing and a couple of inches of insulation. And it still gives me a problem with the tub.

    So i figure no matter what, the vent has to run horizontal for a couple of feet regardless. As long as the vent goes "uphill" from where it's taken off hat diff will it make if it's 3 feet or 8 feet run horizontal before it hits a vertical vent pipe into the attic?

    Here's some pics of the old layout and pipes

    original bathroom.jpg
    shower to vent.jpg
    drain and vent old.jpg
     
    Last edited by a moderator: Apr 26, 2015
  5. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    I'm a little confused by the pictures.

    The lav can wet vent the shower or tub, but you should use long sweep fittings below the flood level.
    What I see are santees and medium 90 bends. Not okay.
    I should be seeing wye fittings, long turn 90's and 45's

    A 2" trap arm can go five feet past the vent.
     
  6. rickz

    rickz New Member

    Joined:
    Apr 20, 2015
    Location:
    Toronto, ON
    Hi and thanks for the feedback so far Terry & bluebinky. I did learn from one of the many previous posts about long sweep fittings and wyes.

    I'm still a tad unclear on how the venting can work so I've simplified the scenario here.

    Assuming I'd prefer to dry vent, the vent takeoff can't be more than 5 feet down the trap arm. Less is better but more than ~4" on 2" pipe.
    I understand there should also be less than one pipe diameter fall from the trap outlet to the vent fitting. That makes sense and would suggest that at 1/4" per foot of fall, somewhere in the first 2-4 feet is a good spot for vent takeoff.

    Having said all that, here is the only viable path for the trap arm/waste pipe. It's 10' from the shower to the existing waste pipe.

    Where/how is this best vented?

    thx!

    shower drain.JPG
     
    Last edited: Apr 27, 2015
  7. cacher_chick

    cacher_chick Test, Don't Guess!

    Joined:
    Jan 5, 2008
    Occupation:
    Test, Don't Guess!
    Location:
    Land of Cheese
    The shower vent either rises vertically within the shower wall or the drain is routed to one of the room walls to allow a vertical vent take-off there.

    Alternatively, the lav drain runs to the shower drain, which wet vents the shower through the lav vent.

    The shower drain in any case must be 2", and if you wet vent through the lav, the lav drain must also be 2".
     
  8. rickz

    rickz New Member

    Joined:
    Apr 20, 2015
    Location:
    Toronto, ON
    Thanks cacher_chick.

    The way I see it I can't go to the side in this latest picture to the inside wall since the joist holes will be too close to the top of my lovingly sistered joists. I can't go in the opposite direction from the drain/trap since it's an outside wall (i *could* make that work since that wall is going to be 7" deep and insulated).

    And no matter which way I go I have to pull the vent off the trap with a sideways rotated wye and run horizontal for a fair distance to get to a vertical location because of clearance under the subfloor.

    So I'm concluding I am hopelessly lost, since I can't be the first to have faced this problem. Another crazy idea I dreamed was to take the vent off the trap and run above the floor through the shower curb. That seems really odd to me.
     
  9. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Had you thought of adding a shower bench? Probably won't work, but I thought I might throw that out.
     
  10. krik

    krik Member

    Joined:
    Dec 31, 2014
    Location:
    Maine
    How about this: run the lav drain (2") horizontally through the wall to the outside wall, make a 90, run horizontally some more and then go down in the outside wall. This' would allow you to wet vent the shower. Not sure if you can meet cleanout requirements that way, though. Also not sure how you'd then vent the tub, although (and I'm not sure if this is necessary or allowable) you could drain each sink separately and run two wet vents - one for shower and one for tub.
     
  11. bluebinky

    bluebinky Member

    Joined:
    Aug 31, 2011
    Occupation:
    Electrical/Embedded Software Engineer, Retired
    Location:
    Des Moines, WA
    I'll probably get yelled at for even mentioning this, but what about going to a larger drain size? 4" will allow a 10' trap arm, if I remember right...
     
  12. rickz

    rickz New Member

    Joined:
    Apr 20, 2015
    Location:
    Toronto, ON
    Some great brainstorming! Thanks.

    What I could do is this.... The horizontal rise is adequate, but not ideal. It's just a tad higher than the trap arm as they parallel each other based on how much I can rotate the wye before everything bumps up to the subfloor [not shown] ;)
    IMG_1667.JPG

    or this nasty variation:
    IMG_1668.JPG

    and this just won't work since that's where the vanity will be (not to mention it is above the floor:
    IMG_1669.JPG
     
  13. krik

    krik Member

    Joined:
    Dec 31, 2014
    Location:
    Maine
    Use the first variant and make it a wet vent. I don't believe you'll be able to get a code-compliant dry vent in there without a lot of acrobatics, if at all.
     
  14. rickz

    rickz New Member

    Joined:
    Apr 20, 2015
    Location:
    Toronto, ON
    I prefer option 1 as well, however I have nothing else to wet vent it with. It'll be a dry vent. I could run the trap back to the same black wall, but it's an exterior wall, which means the drain to the basement will be on the drywall side of the insulation, but exterior none the less.

    Anyone have any other ideas?

    signed - stumped in Toronto
     
  15. cacher_chick

    cacher_chick Test, Don't Guess!

    Joined:
    Jan 5, 2008
    Occupation:
    Test, Don't Guess!
    Location:
    Land of Cheese
    Is the shower going to have any walls? If so, you run the drain under the wall to provide a proper vent. I am not there to see it in person, but it looks to me like you can wet vent properly. You will have to drill through the joists. The wet vent through the lav does not require the wye to be rolled up- it can be flat. Vents can be run within outside walls where necessary. They do not hold water and thus are not in danger of freezing.

    As far as I can tell, your options are to change the layout, modify the framing so the piping can run through it, or do it wrong.
     
  16. bluebinky

    bluebinky Member

    Joined:
    Aug 31, 2011
    Occupation:
    Electrical/Embedded Software Engineer, Retired
    Location:
    Des Moines, WA
    Just to clarify, any pipe more than 45 degrees from vertical below 42 inches high is not a vent. None of the three latest "variations" are vents.

    Without being there and really seeing, I might run the trap arms to the "far" wall and then hide the drains above (in) the kitchen cabinets around the perimeter. This seems to be a fairly common dilemma, and a "correct" solution is not always easy or pretty...
     
  17. bluebinky

    bluebinky Member

    Joined:
    Aug 31, 2011
    Occupation:
    Electrical/Embedded Software Engineer, Retired
    Location:
    Des Moines, WA
    One more option is to run the trap arm to the far wall, take off the vent up the wall, and then turn the drain around and go back the other way. You'd have to figure out how to do cleanouts...
     
Similar Threads: Perplexing layout
Forum Title Date
Plumbing Forum, Professional & DIY Advice Perplexing water hammer issue Sep 7, 2020
Plumbing Forum, Professional & DIY Advice Perplexing PLX Jun 9, 2007
Plumbing Forum, Professional & DIY Advice Hoping to get some feedback on my DWV layout. Wednesday at 10:32 PM
Plumbing Forum, Professional & DIY Advice Need DIY advice on bathroom DWV layout Oct 14, 2020
Plumbing Forum, Professional & DIY Advice Spinning a Toilet 90* for Better Access & Pipe Layout Sep 28, 2020

Share This Page