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I'm remodeling the washer room and have a question bout my drain and vent pipe. I'm buying new units and I want to extend the drain pipe to the back of the washer. Currently it's on the side close to the front of the washer. The picture shows on the left what it use to be. Once in a while it would back up and spill out. So with the new units coming and wanting to go 2", I was thinking of breaking the cast iron vent, put in a rubber tee and capping the old 1.5 drain pipe. I'm not going to try and fit it in the wall so it'll exposed. Vent pipe will then go 1.5 up out the roof. What do you guys think? enter image description here

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It's not going to be that simple. Unless you support the pipe above where you want to put the rubber boot, it's likely going to come crashing down. Depending on what's above, you might be better off cutting the cast iron where you want, and replacing everything above the cut with PVC/ABS. Without knowing more about what's above this, and what else ties into that pipe, there's no way to provide an accurate answer.

I will say that the rubber boot, is likely not the best course of action.


  1. Remove the galvanized pipe.
  2. Use a chain break to cut the cast iron a bit lower than you planned.
  3. Install a Fernco coupling to transition from cast iron to PVC/ABS.
  4. Finish the plumbing in PVC/ABS, including the tee for the standpipe trap arm.
  5. Properly support PVC/ABS plumbing.

enter image description here

Make sure the trap arm for the standpipe is not too long for the size of pipe you're using (2" pipe = 8' max. developed length trap arm 1.5" = 6'). Also make sure the drain has the proper slope.

  • To replace the galvanized pipe above the cut is the plan. There is nothing else tied to it. Straight out to the roof. First cut galvanized pipe and then cast iron. Is there a better way instead of the rubber boot? – al the man Mar 3 '16 at 21:25
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    @altheman sorry, you didn't mention replacing the steel pipe in your original post. A rubber boot (Fernco connector) can be used, it just can't support cast iron and steel pipe. – Tester101 Mar 3 '16 at 21:52
  • Sorry, ok so Tester101 explained it well and corrected what my thoughts were. If stand pipe and trap arm are 2", they should be able to extend up to 5' or should I use 1 1/2 for stand pipe and trap arm up to 3'? And I assume capping old stand pipe is OK? – al the man Mar 3 '16 at 22:14
  • You can use 2" pipe and the trap arm can be up to 8' long, or 1.5" pipe and the trap arm can be up to 6' long. Use whichever you want, just don't make it too long. I thought you mentioned using 2", that's why I used that. There should be no problem capping the old standpipe. – Tester101 Mar 3 '16 at 22:25
  • OK, Thanks. I just hope the cast iron does crack when it breaks off. Thanks again! – al the man Mar 3 '16 at 22:31

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