If you hear an occasional "psst" type of hissing sound coming from your toilet tank, it's your fill valve giving you a signal that it is continuing to try to fill your toilet tank even though it should have automatically shut off.
Without the slight hissing sound, you would probably not know that your water is continuously flowing into the tank because it simply spills into the overflow tube in the tank. However, you would definitely know something is wrong when your next water bill arrived.
If the fill valve is running continuously, it is probably simply defective or has outlived its lifespan, but if it is running intermittently and making the occasional hiss sound, it is likely that the internal float is corrupted by sediment, mineral deposits, or rust from old galvanized supply pipes.
How does a tower type fill valve work?
All fill valves have a float that rises with the water level in the toilet tank and triggers an automatic shutoff when the float reaches a set point in the tank. Traditional style tank fillers use an oval black hollow ball that is attached to the fill valve by a metal rod. The ball is positioned atop the water so it rises with the water level. The metal rod acts as a lever and activates a shutoff button atop the fill valve.
Tower type fill valves have floats inside their bodies that trigger water shutoffs when the water level rises inside the bodies of the valves. These types of fill valves are much more compact than ball valves, taking up much less space in a small toilet tank. Unfortunately, this design also leaves the valve float vulnerable to clogging as deposits build inside the valve.
Removing the old valve
You'll need to shut off the supply valve that controls the flow of water to the toilet. Next, flush the toilet a few times to drain the tank as much as possible.
You'll likely need to absorb any remaining water with a rag or paper towels. When the tank is empty, loosen the nut that connects the supply line to the bottom of the left side of the toilet. You may need an adjustable wrench to loosen it.
The supply line will be filled with water, so keep rags or paper towels handy. After removing the supply line, you will remove the large plastic nut that holds the fill valve in place inside the tank. It should only be hand tightened against the bottom of the tank. After removing the nut, lift the fill valve from the tank.
Installing the new fill valve
Check the manufacturer's instructions before positioning your new fill valve because they may vary in design. However, they all install the same way. Place the threaded end of the fill valve through the hole in the bottom of the tank, and secure it with the large plastic nut. Hand tighten the nut only, because using a wrench could crack the porcelain tank.
Wrap a strip of Teflon tape in a clockwise direction around the threads at the end of the fill valve and connect the supply line nut to the threaded connection. You can use a wrench on the supply line, but hold the fill valve in place so you don't spin it out of position.
You will need to adjust the valve according to the manufacturer's instructions. Adjust it so that the water level rises to one inch below the top of the overflow tube in the center of the tank.
Turn on the supply valve, clean up your mess, and you're finished. For more information, contact The King's Helper or a similar company.