Tying into 3” stack

[jahvette20]

Hello,
I just joined to ask this question and appreciate the feedback. I’m in the process of remodeling a 3rd floor apartment and would like to move the bathroom. There is a 3” cast stack that goes from the horizontal 4” main in the basement (y combo connection) all the way through the roof. There is only 1 double 45 off set at the top of the foundation and the rest is vertical other than it runs horizontal in the attic for a bit. The only thing it drains now is a second floor bath (toilet/tub/sink). The toilet basically drops directly into the stack (maybe 2’ horizontal), the tub is about 3’ run, and the sink about 6’. There is no other venting for these fixtures. I don’t know what the tie in fitting to the stack is because it is not expose. It would be a lot more work and inconvenience to the second floor tenant if I need to tear up her bathroom to ad venting. If it were a 4” stack I don’t think I’d even be questioning it, but tell me if I’m asking for trouble just cutting in a sani T and adding my bath. The new bath would have toilet 18” to stack, tub 6’, sink 4’. I could always vent these if needed. Honestly, I don’t care as much about local code as I do about creating future problems.

 

[Sylvan]

send a picture

 

[Sponsor]

 

[Breplum]

When the stack is venting lower floors, then you cannot by code put a tee on a higher floor to add plumbing because the lower floor venting is affected.
The code is designed to protect public health/safety. The slug of water traveling down the stack can create problems.

 

[Jeff H Young]

As long as the connection is below the connection of the other bathroom only the new bathroom will need venting or aav the existing bath room would be fine