A leaky toilet led me to take my toilet off the floor and found a broken, leaded, cast iron flange on a 4" pipe not secured to the concrete floor, just leaded to the pipe. I have since taken the flange off and cleaned the pipe as well as I can. A friend recommended a replacement cast iron flange with a rubber gasket that can be torqued down so that I don't have to re-lead. I was given a "Code-Blue" 4" x 4" deep cast iron flange. It will fit, but I could use the 2" version, which would seem more stable in my situation. The pipe comes up through asymmetric cast concrete and will not support a new flange being screwed to the concrete since the cast is too wide. Should I back-fill this with hydraulic cement and proceed with the 2" deep replacement flange and screw the new flange into the new concrete? Or should I just put the new flange on, don't screw it in and replace the toilet? This is the way I originally found it...my house was built in 1960. I have included pictures.







Edited 2 times.

since you seem to have a little time to do this, i would fill all around the pipe with hydraulic cement right up to the top of the tile. clean the inside of the cast iron really well and use a flange that inserts inside the pipe. push it in so it sits ontop of the tile. use some tapcon screws to secure it to the floor.