Korky quietfill maxperformance whistling

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?

WP typically rises in the middle of the night for two reasons: they're refilling the towers and need the extra pressure to get it there and there are far fewer people using water then. So, your 'nominal' 80psi could be a lot higher at some points in the night. Plus, depending on the city where you are, you might still have a closed system (a checkvalve either in or near the meter or who knows where) and need an expansion tank. I've heard that many places now require a ET, regardless of whether you have a closed system, as most places are installing them as their meters get replaced over time. Excessive pressure will create significant ridges as the seal gets excessively compressed.


A new cap

Thanks for the good points. It seems like I should start with installing an expansion tank. Any requirements on how close to the water heater it should be placed? I don't have a lot of room from the top of the heater to the ceiling.

Code says the ET should be between any shutoff and the WH; IOW, it can be anywhere, but there should be no way to isolate it from the WH so it can always do its job.

Not sure there's any point in installing an expansion tank unless you also install a PRV. I know 80 psi is "normal", but it's way higher than necessary especially when it is probably even higher at night. 50 to 60 psi is plenty high enough, and many home are fine with less than that.

At 80 psi I would not bother with a PRV, and without the PRV, ( or a check valve in the supply line which is rare), an expansion tank has absolutely no purpose. You have a defective fill valve, but I never use the Korky one anyway.

My point is that if your daytime water pressure is at 80psi, and you don't leave a peak reading gauge on it overnight, you have no idea what the pressure is at say 3am, where it could be quite a bit higher.