Is it OK to use a rubber gasket under my disposal sink flange?

Question

My brother in law has a GE GFC520V garbage disposal that appears to be leaking from the flange that connects to the sink. The fiber gasket that is under the sink is swollen and falling apart. I was able to tighten it by hand and it "squished" out the fiber gasket.

There appears to be repairs that were done with the previous owner; plumbers putty / pipe dope that are slapped up there by the support ring.

My plan was to take it apart and replace the fiber gasket with these gaskets from Home Depot along with the gasket under the sink flange with plumbers putty.

But in reading page 5 of the manual, it appears that there is a Rubber Gasket under the Sink Flange. I was expecting plumbers putty here. The instructions state that a rubber gasket is used instead of plumbers putty with stainless steel sinks.

I am looking for feedback on using plumbers putty instead of the rubber gasket. Or do you think that the rubber gasket is alright to reuse?

Answer 1

There is a term for the installation when plumbers putty is not used. It is called "leaking". I always use plumbers putty. It will mark up a stainless sink, but that cleans off easily when everything is done.

Answer 2

Most likely, the only way the fiber gasket got wet is if water leaked past the rubber gasket above it. Don't reuse the existing one. If you've got a kit with both gaskets, it's probably just fine to replace them both and expect to get about the same life out of the new set.

If you want longer life, replace the rubber gasket with a copious amount of plumber's putty. Carefully clean up any squeeze out.

If, however, the disposal is still under manufacturer warranty, you may want to stick with the manufacturer approved installation method, just in case something more serious were to go wrong with it. That way, they won't have grounds to deny a warranty claim because "you didn't install it according to their instructions".