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? enter image description here


2 Answers 2


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.

  • Totally agree, +1 from me as the magnet from the solution would help the OP in identification of the metal. Sep 2, 2023 at 8:03
  • To the OP - if you get yourself a small propane torch to unsolder that pipe (as opposed to just cutting it), make very certain that the yellow cable is kept far away from the heat! (and remember that the pipe itself will also get hot enough to melt/burn the cable insulation)
    – brhans
    Sep 2, 2023 at 13:35
  • 1
    Thank you, I will try the magnet method and torch. Yeah that electrical cable isn’t in the most ideal spot. I have an electrician coming out to redo everything this week, so I’ll wait until he has that moved.
    – Dylan L
    Sep 2, 2023 at 14:30

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.

  • Thank you! This is just what I was looking for. I hadn't posted the rest of the pipe situation since I was only allowed one photo, but there is a connection to plastic already made where it attached to the garbage disposal. I was hoping maybe I could still keep that intact and reattach once the base cabinet is installed, but if it's easier to just cut the pipe, I can do that instead. i.imgur.com/JwWBLY5.jpg
    – Dylan L
    Sep 2, 2023 at 21:39
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    @Dylan L, YW...often after installing a new cabinet, plumbing things don't line up. This gives you the opportunity to make everything fit correctly.
    – RMDman
    Sep 2, 2023 at 22:34

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