We have old cast-iron pipe for our plumbing waste, but it is rusting out and needs replacement. What can we use instead of PVC?
A great alternative to PVC for waste lines is ABS (Acrylonitrile butadiene styrene) plastic piping. ABS schedule-40 pipe is approved under both the International Residential Code and the Uniform Plumbing Code for DWV (drain, waste and vent) applications and it has the same service life as PVC.
It is my understanding that ABS is slightly easier to work with than PVC as well because it is a one-step process when gluing the joints together (a solvent/primer is not required).
For more information:
You should read architect Michael Heacock's Q&A "I'm seeking bids to repipe my house. PVC is recommended by all three plumbing bidders. Is it safe?"