Moving A Soil Stack

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Bird Doo Head, Jan 30, 2010.

  1. Bird Doo Head

    Bird Doo Head New Member

    Jan 30, 2010
    Hi Everyone
    First, please pardon me if this shows up twice. I thought I posted it, but I think I deleted it by mistake, as I can't find it. Me plus computers equals Trouble!

    Second, I have a plumbing project going and certainly would appreciate any advice you all care to share. I have searched the internet and the library. I tend to get myself more confused than educated.

    I am changing one of our bathrooms to a "wet room" for a family member who is handicapped and can't step into a shower. We will keep the tub/shower. Since I've got everything pretty much discombobulated, I thought this would be a good time to re-locate the soil stack (?) that serves the room. The vertical portion runs smack dab next to my basement "office" desk and the tub/shower drain runs across where I'd like a cabinet.

    What is there now is all schedule 40 pvc until it enters the slab basement floor. The stack is 3" and ends with a sanitary tee that is a 3 x 3 x 3 x 2.
    A) Into the top is a 3x2 bushing with a 2" street 90 and a 1 foot length then a 90 going up into a wall. In the wall, there is a 2 x 2 x 1 1/2" sanitary tee. The tee branch has a 1 1/2 x 1 1/4 marvel, serving the bathroom's pedestal sink. The 2" continues out of the tee and ties to the 4" vent through the roof (last item before exit) which also serves two more bathrooms. (One is also 1st floor & one is 2nd floor, whose sink vents separately).
    B) Into the side 2" branch of the basement tee is a 2 x 1 1/2" bushing. The 1 1/2" goes 2 ft to the tub/shower trap.
    C) Into the 3" branch is the toilet, which is 5 feet away.
    D) The bottom outlet goes straight down into a wye and 1/8th bend under the slab. It ties into a 4" CI. There is a flush clean-out tee about 8" above the floor.

    My Idea:
    A) Get rid of the stack down to the (almost) basement slab. Working from the bottom up, start with a clean out tee. (The existing one is facing a hole cut into my office desk-counter- with a chrome cover inside the cabinet.) Now, instead of going straight up, I would like to 90 it horizontally toward the basement wall and run 2 feet and 90 it back up again. OR: Should I use 45's & street 45's instead of 90's? This would move the stack to the wall of the basement & out of my precious turf.

    B) Spin the 1 1/2" tub/shower trap to aim 45 degrees to the basement wall & wye & 1/8th it into a new 2" (replacing the 1 1/2" that is there now). I'll include a clean out at the end of the wye, like there is now, but 2" This branch will be about 48" long.

    C) Vent the tub immediately after the trap. I can easily tee up and use an AAV under the stairway, 6" above the tub rim, adjacent to the tub valve wall. This area stays accessible as the under stair closet back wall comes off to access some hydronic balancing cocks. I fit in there for service. I also can, not easily at all, take the vent to the stack on the second floor. (Will require a drywall chase in the stair landing)

    D) Since the 2" from the tub/shower to the stack is now vented, I would like to wye & 1/8th the new floor scupper (trough) drain into that 2". The new 2" trap will be 3 ft from the 2" & 4 1/2 Ft total pipe from trap to stack.

    E) Keep the vent from the top of the tee as it is, only moving it over 2 feet along with the stack.

    F) In the process, raise the toilet waste line. It is now, from flange to 4x3 closet ell, about 18" long. Since the flange is broken and must be replaced, I'd like to go with a 3" flange into a 3" ell, but near the sub floor height. Then, at the stack, jog down by rolling a 45 & street 45 (or two 60's?) to enter the stack tee side 3" (the top 3" is the vent fitting). I'd assume using a 90 & street to do this would be problems.

    G) If I decide to use a 3 x 3 x 3 x 2 x 2 tee on the stack, I would have to take the new 2" scupper trap on "tour" to get to the opposite side of the stack. (Trap Draining West-90 North- 18" pipe- 90 East- Stub into Tee)

    H) One last question: Is there a difference between a 3" DWV 90 and a 3" closet ell? I can't find a closet ell at the local home center and a local plumbing supply tells me there is no such thing as a closet bend in 3"

    For the record, there is no possible way to vent the new 2" trap without going horizontally first.

    Am I on the right track with my re-work, or totally misguided?

    I'd like to thank all of you in advance. Of course, I want it to work correctly- but someday I will sell the house and don't want to deliver a nest of problems to a new owner.

    I (think) I've attached a drawing of the proposed layout, but without the jog in the stack.

    Again, thanks to all of you for pointing me in the right direction!

    Attached Files:

  2. dcelite

    dcelite Plumber

    Oct 5, 2009
    Los Gatos, CA
    1) You still need to vent the floor drain. 2) You can not roll the toilet trap arm down to connect to the vent stack as it will create an "S" trap which is illegal.
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  4. Bird Doo Head

    Bird Doo Head New Member

    Jan 30, 2010
    Venting Floor Drain

    Thanks for the good advice!
    Since rolling the toilet trap arm down makes an "S" Trap, I'll leave the soil stack where it is. Sometimes what seems like a great idea goes goofy in the details! But, now I can picture the problem you described perfectly.

    I am stumped, however, about venting the floor drain. I understand that one can not take a vent horizontally until it is above the flood rim of the fixture it serves (the floor?)

    Since the floor drain will be in the "middle" of the room, I can't take off with a vent up the wall for quite a distance. Vent pipe will tee off inches from where the trap arm enters the soil stack. Trap to stack will be about 3 feet as I re-measure it. Is that the way to do this?

    Thanks Again,
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