Flange Extender

I’m renovating a bathroom. The top of the toilet flange sits ½” below a newly finished floor. I was planning to use a flange extender that fits inside the existing closet flange, but someone told me that it was important not to narrow the hole. They suggested a flange riser (aka spacer).

Why? The flange extender narrows the existing flange diameter from 2 9/16” to 2 5/16” still larger than the 2 1/8” toilet trap diameter, the limiting dimension. Why would the extender be an issue for the ~7” from the toilet bowl horn to the 3” waste pipe?

Am I missing something?

It sounds like whomever installed your flange used an internal mount flange on a 3" pipe. This in itself is a problem, as good practice only allows an internal mount flange on a 4" pipe. Narrowing it further is asking for problems as the waste exits the toilet, it is generall in a turn, and needs room to make that turn without slowing. Narrowing it more is just asking for problems.

Hindsight, but the proper time to have addressed this was before the new floor was installed. The proper place for a flange is on TOP of the FINISHED floor, not burried in it. I'd definately go with spacers rather than further narrowing the hole. If I had the option from below, I'd consider replacing the flange and moving it where it is supposed to be and then ensure I used a flange that didn't narrow what sounds like your 3" drainage pipe.

I'd seriously consider having a plumber replace the old flange and properly install a new one. As Jim noted, this is a poor installation you have and you're just gambling on problems. The time to fix it is now before you have a plugged toilet. It will never be easier or less expensive in the future. The spacers will be better than the extender, but still not the best.