The old one has to be removed and a new cast iron one installed. If it is not sealed to the pipe, and an ABS one cannot be sealed, then water will leak out of the resulting groove. Fastening the flange to the floor has nothing to do with sealing it.: My iron toilet flange appears to have been soldered to a 4 inch cast iron pipe. The flange is loose and and still good, but broke off part of the 4 pipe just below where the flange rested on it. This pipe is now jagged. By twisting the flange, I can get it to match back up to the broken pipe and it fits snug, but there is no seal. : I will be raising the floor and need to raise the flange height and would like to replace the old flange with an ABS one. : Can the new flange be place over the 4 pipe and then secured to the new floor or does it have to be secured to the cast iron pipe too? : Any ideas? : Thank you, : Bob
