Cast drain: horizontal to vertical (main stack)

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by JaCkaL829, May 7, 2020.

  1. JaCkaL829

    JaCkaL829 New Member

    Mar 20, 2017
    North Jersey
    I have some older cast iron drain pipe I believe 4” that ties into the main vertical stack that need to be replaced due to cracking from within. This only services a toilet and sink for a powder room. I would like to replace with 3” PVC and follow the same path as what’s in there now. I’m just wondering if I can make the same transition horizontal to vertical that is already there with 3” PVC and a regular 45 elbow? I plan on adding a PVC cleanout in the same place and using a 45 wye that is 4”x4”x3” in the main stack. Let me know if this works or if I should do something else. The span before the 45 downward drop is about 8’ of horizontal that there isn’t a whole lot of room to move around.

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  2. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    3" works for a toilet and lav.
    If you're redoing what you see, I would guess it should be fine. I can't see where you're going from there.
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