I'm in an older house and need to replace a section of pipe draining from the kitchen sink. Two caveats that are relevant, however:

1. There are clearly two different types of pipe. One is darker (I assume galvanized steel), one is lighter, almost like aluminum. Both have corroded to the point of having major holes that are now covered in duct tape, I believe (it's my parents house, I just returned recently for a few months to assist them with some different things around the house).

2. Both sections of pipe have major holes, and the second (lighter) section, goes directly into the foundation. It has holes about two feet from the foundation.

A plumber apparently has looked at it and said that he would use a torch to cut the lower section of pipe off to replace the whole section (sink-foundation). My questions are:
a) How will the new section of pipe be attached to the piece that goes into the concrete floor?
b) What if the pipe develops a leak below where he cuts it later on? Is there any solution to replacing this portion of the pipe without tearing apart the concrete (cutting it right next to the foundation or something similar?)?
c) If I decide to attempt this without plumber-assistance, how should I go about attaching new PVC to the cut off section of pipe?

Hi contentpens:

The darker pipe sounds like cast iron pipe and the lighter colored one like galvanized... like you said... but not super important anyway...

What is important is using the correct transition clamps... see pics. These are shielded clamps (labeled as PROFLEX or as MISSION clamps with complete SS Band)... available at your local home supply store. They will accommodate the difference in pipe thickness between the cast iron (I assume) and the new PVC.

Example here might be to find a 2" cast iron pipe x 2" PVC mission (or proflex) style shielded clamp.

Up near that foundation does sound a little scary... I am wondering what the guy with the CUTTING TORCH was talking about..

I use a sawzall with metal cutting blade when I get anywhere near the foundation wall. Hopefully, reducing chances of disturbing pipe at the foundation wall...

Anyway... there is some info. Get back to me with any questions... MARK

.