I inherited our house that was built in 1972 and was one of the first in the neighborhood where they installed plastic DWV piping. It is gray in color, but is PVC and when I have made repairs with sinks and such it was compatible with white PVC fittings and cement. I want to replace the kitchen cabinets and the sink where we have had trouble with the sink drain line. There is a bathroom above and the stack is in one of the back walls I have to remove anyways. I'm wondering if instead of just the pipes to the sink, maybe I would just replace the whole stack because it is 43 years old. An I worrying over nothing? What is the lifespan of plastic plumbing? If this were cast iron I would definitely call a plumber to replace with plastic but now I am tempted to do this myself because the new stack would be an exact copy of the existing one, just with new plastic. I am going to get a permit for other jobs around the house so I might run this past the inspector too. My sister had her bathroom done over and the contractor used the existing 30 year old plastic pipes, is that standard or cheaping out? If I replace this stack how long does it have to be dry before using that bathroom again (there is another one I can use, on another stack). Do cast iron pipes actually last 100 years? Thanks for your help.