Adding a 2nd floor bathroom - venting and drain questions (see diagram)

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by PerryNotMason, Apr 12, 2021.

  1. PerryNotMason

    PerryNotMason New Member

    Apr 12, 2021
    Portland, OR
    Greetings, and thanks in advance for any input!

    Novice plumber (but quick learner, i think) here.

    I purchased a 1923 house recently that had a leak coming from the toilet on the first floor. Subfloor was rotten, and has since been replaced. There was a hole in the old lead(?) flange, and so I took the opportunity to replace the corroded cast iron vent and drain pipes down into the basement as it was time.

    while I am remodeling the bathroom and have the walls open, I would like to think through how to add a bathroom to the second floor: toilet, sink, shower (no tub).

    I understand I can't drain into the vent stack, and so I am considering placing a 3" ABS pipe in the wall for when I get around to the bathroom install (probably next year) but I am unsure how to connect everything and how to vent the toilet.

    For example, the distance from ceiling joist (future floor joist) to roof is very small - maybe 12-15".

    Here is what I currently have. The black pipe is the original cast iron, anything in grey is black ABS pipe.

    The tub is vented separately with a pipe to the roof on the other side of the bathroom that connects to the main vent stack in the basement.

    any obvious problems with how I did the current repair?
    what is the best way to consider venting a toilet in the second floor?

    Thanks for any input. I can also upload some photos if helpful.

  2. Tuttles Revenge

    Tuttles Revenge In the Trades

    Oct 15, 2014
    A bathroom drain added to the second floor would need to tie in / connect to the stack below the fixtures connected at the first floor because all of the stack above the first floors floor, is a vent. This would also be a good time to bring a dedicated vent up from the basement so that the plumbing from there isn't vented through the drain stack.. and in case you wanted to add more plumbing to the basement.
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  4. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    Sort of like this.

    Tuttles Revenge likes this.
  5. Jeff H Young

    Jeff H Young In the Trades

    Feb 27, 2020
    I dont see a vent stack in basment so whatever down there needs to be vented. the sink at 1st floor has a drain coming from basement then perry shows some box at first floor unclear that depiction. bring a 3 inch line up that branches off below the toilet and tub at 1st floor
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