I have had a Toto Nexus in the powder room for a couple of years. It works very well, but the Gmax fill valve just developed a loud humming sound as the tank fills. The blue gmax fill valve looks different from the ones in our Drake upstairs. The Nexus fill valve is "flat topped" versus the Drake's valve that slopes down in the direction of the flapper valve. Are these valves interchangeable and more importantly, can I just change the top out with one ofthe Lavelle/Korky replacement units from Lowe's?

Thanks very much.

Randy in VA