Which Bad Option Is Best For My New Upstairs Sanitary Drain?

Discussion in 'Remodel Forum & Blog' started by doinmybest, Oct 1, 2012.

  1. doinmybest

    doinmybest New Member

    Messages:
    3
    Location:
    new york
    Hi and thanks for reading.

    Please bear with me as I explain the situation.

    I have a 56 year old cape with a 4" cast iron stack down to the sewer line with, from the bottom-up starting at the foot of the slab:

    1) A 3.5" cleanout

    2) A tee-off for the sink/dishwasher drain, which loops back to the next element ... my guess would be 1.5 or 2".

    3) double tee (same size as the drain in #2), one side is the vent for the sink dishwasher, the other side is the vent for the 2" washing-machine drain that connects below the cleanout via a u-trap buried underneath the slab.

    Of course, somewhere under there is the ground-floor toilet connection, which is directly opposite the bottom clean-out.

    I'm building a bathroom upstairs where there nary 'twas one before ...

    Now of course, the right thing to do would be to have someone who knew what they were doing come in, dig up the slab and give me a new stack coming off at or below where the ground-floor toilet connects to the existing stack.

    Not gonna' happen ... this place had a mold problem that set me back like 30% of my budget already. That was two years ago.

    So the way I see it, I've got two options, neither of them good, but I'd like opinions as to which one would be less bad:

    Option #1: hook into the clean-out at the bottom above the slab. I guess I'll need a 3.5"-3" bushing. Interesting side question: the cap is brass but the pipe is iron, **** things really rusty as it is ... should I use a brass or an iron bushing?

    Option #2: tie-into the pipe from above (cut at a point between the floors, add a fernco). I thought about this and it would seem to me that if there's a toilet draining from above, that I'd have to cap the two 2" vents that I described, as since there's no water flowing through them, then this would create an unsanitary condition. I'm hoping that since there's water flow through the 2" connection below that for the kitchen sink and dishwasher that what I'm worried about for the vents wouldn't apply. I'd reconnect the vents of course, but above the upstairs drain tie-in.

    Looking forward to any and all criticism. No feelings left here to hurt
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,843
    Location:
    Cave Creek, Arizona
    quote; should I use a brass or an iron bushing?

    It is immaterial, because you will not find either one. If you disconnect the two vents from the cross and connect them back in upstairs, (and do it properly), and THEN add a vent for the downstairs toilet, you will have a legal connection, but it would be more difficult to do than to make a proper connection beneath the floor into the 4" main line.
  3. doinmybest

    doinmybest New Member

    Messages:
    3
    Location:
    new york
    Thanks for the reply hj.

    The reason I'm not going downward is that I'm on a slab and don't want to risk digging up the concrete and cutting the old iron that's down there.

    When you say that I'd be legal if I reconnected the two 2" vents properly, what issues come to mind? My intent on one of them was just to extend the 2" vent run as far up the stack as I needed to to get above the new wet connection -- turns out I have another option on the other one, an existing 3" pvc tie-in above all this on the 2nd floor (long story that I'll spare you).

    Just out of curiosity, I take it that the new wet-tie-in necessitates the new vent for the downstairs toilet to be legal ... my guess is to why this is would be because if there's water coming down the stack from upstairs when the downstairs toilet is flushed then the venting of the downstairs toilet is interfered with ... do I have that right? ... or are there other issues that I haven't considered?

    Thanks again!
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,154
    Location:
    New England
    To remain a vent, it must be connected at least 42" above the floor or 6" above the flood plane of the drains above it, whichever is higher. You need a clear path to the vent through the roof that won't be full of waste draining down to block it. Again, once a vent, always a vent...once a drain, always a drain.
  5. doinmybest

    doinmybest New Member

    Messages:
    3
    Location:
    new york
    Thanks for the info jad'
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,843
    Location:
    Cave Creek, Arizona
    quote; The reason I'm not going downward is that I'm on a slab and don't want to risk digging up the concrete and cutting the old iron that's down there

    THere are a lot of things we "do not want to do", but usually the choice is either do them, or forget the project. IF you don't want to "risk" it, call someone who knows how to do it properly.

    Re. your screen name doinmybest, it recalls the football coach whose team was getting savaged. He turned to the player next to him and said, "Go in for Davis". The player replied, "Okay, coach, I will do my best". The coach told him, "Sit down. The Davis is already doing his best and that is not good enough".
    Last edited: Oct 3, 2012
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