How do I remove the fitting for this drain so that I can fit a base cabinet over top?

Question

Let me start by saying I’m in no way a plumber, but I know some basics to get by and hoping this is something I can tackle myself. I just want to make sure I know what materials I’m dealing with, what fittings I would need, and any potential problems I may face before they happen.

I just demo’d my kitchen and was left with this drain pipe that connected my garbage disposal to the drain. Im hoping I can disassemble it enough so that I’m left with a straight pipe so I can get the new base cabinet in easily when the time comes.

This house is over 100 years old, so I believe this may be cast iron? Does that look correct? It also looks like it may be a little corroded. How would I go about getting this fitting off without having to cut the pipe? Would I use heat the same way I would for a copper pipe? Is there then a specific kind of fitting I would need to reattach a pvc pipe to it?

Answer 1

The house might be 100 Yr old but the pipe installation was made from copper using soldering.

It does not look like cast iron pipe, more like heavily oxidized copper.

Regular copper soldering tools should work. Give it a test with some sand paper removing the patina to see.

What gives it away ? The pipe thickness is more like copper than cast iron which would be much thicker.

A magnet would stick to cast iron but not to copper.

Answer 2

Taking the copper apart is unnecessary extra work.

Unless you want to practice your sweating technique, just cut the vertical pipe high enough to have at least a couple of inches sticking up through the floor of the cabinet.

Then use a proper sized Fernco fitting to attach new PVC to the copper. The shielded type may be overkill, but it is insurance if you have aggressive people that indiscriminately shove things under the sink. In most areas the shielded connecters are allowed inside walls. You don't have that situation, so you have gone above and beyond.

In my area inspectors allow fernco when connecting dissimilar materials. However they don't allow the flexible or Fernco P-traps.

If you un-solder and reconnect the copper elbow and pipe, you are still tasked with connecting to PVC for the rest of the drain. Shark bite and other larger sized fittings to make that connection are difficult to find. Take the easy route.