Replacing Cast Iron Drain Pipe - Vent pipes?

[ricseay]

I need to replace the cast iron drain pipes under my house. I will need to replace plumbing for two toilets, lavatories and tubs. My biggest concern, the vent pipes that extend through the roof are also cast iron. Not sure how to deal with those. I would assume the newer pvc pipe I am installing would not support the weight of the cast iron vent pipes. Look forward to your advice.

 

[phishfood]

The very best option is to replace all of the piping, vents included. If this is not a viable option, than you at least need to replace the stacks from the drain arms downward. And you will need to install riser clamps on the vents before you cut them.