Replacing a float cup fill valve will stop the sound that comes when an old float cup that keeps letting water into the toilet tank.
Step 1 - Remove Old Valve
Start by turning off the water to the toilet by turning the valve in the pipe running to the toilet. Flush the toilet to remove most of the water and then mop up any left in the tank with a sponge. With a wrench, remove the water line from the toilet tank and take off the bolt that keeps the old float cup fill valve in place. Remove the valve and then clean the area where it had been sitting in the tank.
Step 2 - Fitting New Valve
Start by adjusting the height on the new float cup fill valve so the top of it is 1 inch above the top of the overflow tube. Now push the valve fully into place and tighten the nut to lock it in place. Be careful not to over tighten.
Reconnect the water line to the toilet and then attach the refill tube and the angle adapter to the valve. Lock the top valve by turning the lugs slightly. Turn on the water and allow the tank to fill then adjust the float cup to alter the water level in the tank.