Is there a way to fit a 4x3 offset closet flange to the "inside" of a 3" pipe? I'm having a hard time chipping away at the old PVC fitting. If yes, would expanding foam work to fill in the gaps to make the pipe fit?

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Not that this is recommended and not code approved even in Florida.

It reduces the internal bore of the pipe to approx. 2-1/2". 3" is minimum pipe size for a toilet.

I would think pretty good potential that it would cause stoppages.

Pay now or pay later. Keep chipping away.

I would not do it and don't recommend it.......but you asked.

Blockages did cross my mind. Ok better question. Is there a better way of removing the rest of the old PVC fitting from the pipe? The whole thing is looking like a burnt marshmallow from the heat gun. I've managed to get the flange to sit not quite halfway down so far.

if you can get the flange to slide on one inch instead of the full 1 1/2 inch, as long as you can prine and glue it really well, its not perfect but should give you no trouble.
make sure the flange is well secured with stainless screws

"Probably" will give you no trouble.

? Since you are having difficulty performing a plumbing task juuuuust perhaps hiring an actual plumber would be wise ?

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

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The best methods to remove the fitting is using a rabbit or cut along the edges making multiple cuts every 45 or 90 degrees then pry off with a flat head screwdriver finessing it. If it's already mutilated or deformed with a torch I would say your best bet is to go below and replace the entire closet elbow.

There are 3" inside for retrofit flanges for hail Mary situations but in your case you said offset flange that's even worse. I would redo the closet elbow to the right place to avoid the offset flange then install the flange.



Edited 1 times.

A picture is worth a million words.....

Funny you should say that because my uncle had a friend who is/was a plumber come over this morning. Five minutes later and it's set. Soooooo I'm just gonna go sit over here in the corner now and leave things alone.. lol.

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

It is not recommended to fit a 4x3 offset closet flange to the "inside" of a 3" pipe. Closet flanges are designed to fit securely on the outside of the pipe to create a proper seal. Trying to fit a larger flange inside a smaller pipe can result in leaks, unstable connections, and potential issues with the plumbing system.

Also, expanding foam is typically used for insulation or filling voids, but it is not suitable for creating a reliable, watertight connection in plumbing applications.

To properly address your situation, it's advisable to remove the old PVC fitting and replace it with the appropriate 4x3 offset closet flange designed for outside fitment on a 3" pipe. Chipping away at the old fitting can be challenging, but there are tools available that can help make the process easier, such as a PVC pipe cutter or a reciprocating saw with a PVC blade. These tools can allow you to remove the old fitting more efficiently. If you're inexperienced with this type of plumbing work, it's best to consult a professional plumber.