I have a korky quietfill maxperformance fill valve that is about 6 weeks old. The trouble is that it is making a whistling/screeching sound when filling usually loudest right after the flush. Valve stops filling normally. I already tried cleaning the internals and called korky for help. They agreed to replace the valve, but I am wondering what the failure actually is. Shutoff is fully open. The cap seal seems to have pretty deep gooves in it from the top of the riser tube. My water pressure is around 80 psi (unregulated). I am thinking higher pressure equals deep grooves in the cap seal. I probably should install a PRV and expansion tank, but need to call the water company out to use the curb stop and replace the shut off after the meter in the house at the same time (rather have a ball valve). How do these grooves get realigned if you remove the cap to clean the seal and filter?