I have a cast iron toilet flange that is approx 1 in below a concrete floor and is not level. On inspection I noticed one of three bolts around the rim is missing. In addition the concrete has decayed to approx 1 inch of a space all the way around the edge of and below the flange. The previous installation had double stacked wax rings but obviously this was not a good solution. My questions go something like this.
1: How much support does the flange need? In other words if I replace the flange with a twist and set type will the pipe support be enough or will I need to repair the concrete first?
2: How hard is it to remove and replace the old flange?
3: Is it supposed to be flush with the floor or lipped on top?
4: How feasible are the repair plates that span the hole allowing you to mount the flange higher up? Are these for wood floors only?
I am a very capable handy man but have little experience with this type of repair. You might suspect and be correct in assuming I am trying to make repairs without concrete work but will have to do it if needed. Thank you very much in advance for your help!

Hi Mcgyver...

1) Twist and set would require you to pour a hydraulic cement under the flange and then attach the flange into the hardened cement using TAPCON concrete screws (See image).

2) An old cast iron flange should be broken off using a COLD CHISEL and heavy hammer. Here, cast iron cracks so you would drive the chisel down at the weak points in the existing flange (where the bolts slide in) trying to crack longitudinally. You would make two breaks like this and then you would pry the cracked flange up and off the cast iron pipe (*hint* put a towel inside the pipe to keep from dropping anything in/down the pipe).

3) New flange can be just flush, but in most areas we install them so they sit ON TOP of the finished floor. Here, if was tiled floor, when the tile dried you would drill through the tile and screw through the flange/tile and into the hydraulic cement using those tapcon screws for real good job.

4) Repair plates work pretty darn good, but I would need a picture of your flange to know if they would seal properly to the old flange, OK?

Back to you...

Mark