Quieting down a noisy gravity flush toilet requires you to replace the old ball cock valve in the toilet with a new, more modern fill valve. An old ball cock valve has a large float that attaches to the end of a metal rod, which also attaches to the ball cock. The valve on the ball cock closes slowly as the float rises, causing the noises while the toilet refills after a flush. New fill valves keep the valve completely open until the tank fills up with water, meaning the noise of a filling tank takes less time.
Turn the handle on the toilet's water valve clockwise until it is hand-tight. Press the toilet's handle to flush it once, draining most of the water in the tank.
Remove the toilet tank's cover and carefully set it aside. Use a sponge and bucket to remove the remaining water from the toilet's tank. Place the bucket under the toilet's tank to catch water that drips out.
Use a wrench to unbolt the water line from the bottom of the toilet's tank. Hold the base of the old ball cock with a wrench if it twists inside the tank, keeping you from unbolting the water line.
Press down on the ball cock as you undo the nut on the underside of the tank, which holds the ball cock in place. Remove the old ball cock. Use a tape measure to measure the height of the overflow tube in the tank.
Adjust the new fill valve's height to match the height of the overflow tube by twisting the top of the fill valve. The critical height mark on the fill valve should sit 1 inch above the top of the overflow tube.
Twist the cap off the top of the fill valve and thread it into the bottom of the tank. Thread the retaining nut onto the bottom of the fill valve, then bolt the water line onto the bottom of the fill valve. Twist the cap back onto the fill valve.
Insert the fill tube onto the top of the fill valve. Clip the adaptor piece to the top of the overflow tube, trim off the overlapping fill tube and slide the tube onto the adaptor piece. Turn the handle on the toilet's water valve counterclockwise.