For some reason, the builder put in the toilet flanges in my 5 bathrooms so that the top of the flange sticks up 3/4" above the tile floor. The toilets he put in apparently had a deeper inset and did not rock. As I am replacing the toilets, I find that new toilets have only a 1/2" recess around the outlet. This makes the new toilet sit 1/4" above the tile floor. (3/4" protruding height less 1/2 " recess). A also need about 1/4' for the compressed wax ring, leaving me 1/2 " from proper seating of the toilet.
The sewer outlet pipe is 4" ABS, coming up through the concrete slab. The ABS flange is glued to the *outside* of this pipe. The flange is not screwed down, just sitting there.
I propose to cut off the flange/pipe level with the tile floor, using an angle-grinder. I will then glue an *inside* flange into the 4" pipe. The new ABS flange is 3/8" thick and will sit directly on the tile floor. I should gain 3/8" using this approach, which should be enough to seat the toilet properly.
Does this make sense?
Walter