Have an older home (late 19th century) wanting to add a bathroom to the 2nd floor. There is a exposed main vent stack(4") and I want to tie into it with PVC. How can I properly remove the connection joint without destroying the cast pipe?

Have an older home (late 19th century) wanting to add a bathroom to the 2nd floor. There is a exposed main vent stack(4") and I want to tie into it with PVC. How can i properly remove the connection joint without destroying the cast pipe?

Not quite that simple. Do you have vents in your home? Will this job be permitted and inspected? Where do you live and will this job go in by your local and state Plumbing Code? Talk to me. B ack to you, Tom