So I searched and read

shimmy25

through the forum and I think I have a game plan. Basically the problem is when the toilet is flushed and then the bath sink is turned on water is leaking
from the vent pipe. I want to cut the vent just above where the two arrows are, remove that section from the cast iron and use pvc to repair the section. Any suggestions?

bigMikeB

Call a plumber, lead work isn't a DIY repair unless you have done it before and know what is going on.