Hi Mjfdc..

If you are asking about cutting into a vertical cast iron iron stack and inserting PVC in between cast iron sections then the answer is NO. The weight of the cast iron above the PVC could one day crush/shatter the PVC and that could lead to a dangerous situation should the entire stack above come crashing down on someone... ;)

If you are asking about cutting a horizontal section of cast iron drain line and replacing it with PVC to the fixture the drain picks up then YES, you can do that using a shielded PVC x Cast iron clamp... see images.

What exactly are you trying to do?

Let me know more, OK?

Mark

Hi Mark,
Thanks for your help.
It is a piece of vertical pipe that is about 2' long and comes off my tub drain. It doesn't appear to be bearing any weight, except for its own. The problem is that it ends into a 90 degree elbow that is on a slight downward slope. It comes off the tub drain into my basement and drops down to the elbow that then travels about 3' into the main drain. My tub has backed up (doesn't help that I have 3 teenage daughters with long hair and no concept of plumbing) and I think I need to cut the pipe and install a 45 or 60 degree bend to allow proper flow.
Any other suggestions, or do you think I can go with the PVC?
Mike

Cut the pipe using a sawzall with a lennox diamond sawzall blade if you can find it, or any carbide tipped blade will do, too. Then, use the appropriate shielded clamp and go with the PVC... ;)

Mark

Thanks Mark!

:)