Working on a house in NY built in 1948. Sencond floor bathtub was replaced with a newer. The old bathtub waste exit was at point A. Builders cut into upper portion of joist to accomodate pipe to exit point. New tub bed sits lower. Necessary to connect waste exit at point B of "venting system". The "venting system" depicted does, in fact, cut into the top of the first floor.
1. Is it ok to replace the entire length of bathtub vent pipe (the first vertical pipe in image) ?
2. If "1." is yes, is it ok to replace with PVC ?
3. Replace only the section near area B of the bathtub vent pipe by cutting a section in that area and using some type of coupling system to tie into the metal portion above ?
4. If "3." is yes, then what type of coupling system do you recommend.
5. It the bathtub vent pipe even necessary ? I.e. is it ok just to tie into section B, ommitting the entire pipe section above?
6. Would you provide any other recommendation/suggestions