Afternoon all,

I have a 1960 edition house with about a 50- 50 mix of cast/ pvc drain plumbing, with a vent stack that resembles galvanized pipe.

Due to some cast deterioration (flaking into the vent line), I'm considering replacing all the cast in the spring.

Is there a legal connection that would allow me to leave the stack in place?

If not, would it possible to pull the vent out from the roof and reinstall PVC in the opposite order? Under normal conditions, would the vent be supported inside the walls or would anything preclude reinserting PVC?

Thanks for your time.