I need to remove the existing PVC to cast iron adapter in the main waste outlet of my basement. Another PVC fitting will be added in place.

This is a 4" cast iron with a rubber ring that seals between the PCV and the iron.

Here's what I've done:

  • PVC pipe will rotate freely in the rubber.

  • PVC pipe will deflect left/right up/down a few degrees without much force.

  • Added some soap as lubrication. This made the above 2 things a bit easier.

  • Pulling outwards: it won't move at all, even while pulling and rotating/wiggling at once.

I had imagined that this was a straight pipe passing through a rubber "donut" but after what I've tried so far, I'm not sure. It feels like something solid is preventing it from pulling out.

I could cut the PVC apart as I don't need to reuse it. But I don't want to damage anything inadvertently (especially the cast iron) and would rather do it right if that is possible.

Thanks for any advice!

enter image description here

  • Is that a cap on the cast iron fitting? Can it be rotated? Can you pry the rubber seal out?
    – JACK
    Jan 11, 2020 at 17:46
  • @JACK I will take another look but it appeared to be all one piece Jan 11, 2020 at 17:49
  • 2
    The large plastic adapter could be broken up with a hammer and a chisel. Cast iron pipe like what you have here is nearly indestructible, so unless you start wailing on it with a sledgehammer, there should be no problem damaging it.
    – jwh20
    Jan 11, 2020 at 22:14
  • pull on the rubber part, as it stretches it gets thinner and will let go.
    – Jasen
    Jan 12, 2020 at 9:29
  • @Jasen thanks - I thought the same but although I could stretch it a lot nothing I could do would produce any total net movement of the rubber part. Jan 12, 2020 at 10:40

2 Answers 2


If it's all one piece I'm inclined to believe you have a donut and coupling similar to the ones below installed in you cast iron pipe.

enter image description here

enter image description here

I have only used these one time, but I had to hammer the piece of PVC into to rubber donut because it fit so tight. Some PVC fittings have a lip at the tip, like the one below, that would make it harder to remove once it was installed. I think you're going to have to work it out, pulling and twisting, using a lot of elbow grease.


It ended up that I decided to cut the fitting apart. Nothing I tried could budge it outwards at all, though as noted it would wiggle around in other directions; so this started to convince me there was a "connection" inside more than just friction.

(I tried pulling, rotating, using a 4" lever, vice grips, etc.)

I cut the PCV with a demo saw in 2 places and then broke it out with a screwdriver & pliers. It did indeed have a lip which extended in beyond the rubber gasket. This photo shows a similar type of lip:

enter image description here

I didn't get a pic of the actual fitting because I didn't want to take out my camera in such unclean conditions at that point.

In conclusion I am not sure what the "right" way to remove this would have been (without cutting it). Maybe there is no way because the rubber's friction to the metal far exceeded anything I could use to pull on the rubber. Probably a plumber would know the right technique! But, because DIY.

Edit: In hindsight I realized I never tried heating up the PVC. I bet that would have done it. An electric heat gun can get PVC to become "floppy" and I'd done this in other circumstances.

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