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

[PerryNotMason]

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.

 

[Tuttles Revenge]

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.

 

[Sponsor]

 

[Terry]

Sort of like this.

 

[Jeff H Young]

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