Most residential toilets utilize one kind of valve for flushing the bowl and another kind for filling the tank. Flush valves must be manually activated, while fill valves open and close automatically. There are only two basic types of valve mechanisms for each of these operations. Toilet valves used for flushing are typically either a flapper or siphon style mechanism. Fill valves are generally activated by either a float ball or float cup device.
Flapper style toilet valves are usually made of rubber and fit over a large opening in the bottom of the tank. This valve is attached to the toilet’s flusher handle by a chain. When the flusher handle is depressed, the chain opens the flapper valve and allows the water in the tank to enter the toilet bowl at a high velocity and flush the contents of the bowl. Flapper style toilet valves are the most commonly used type of flushing mechanism. These valves have a tendency to become misshapen over time and leak.
Siphon style toilet valves have been used for over a century in residential toilets. When the flusher handle is depressed in this type of flushing mechanism, the tank water enters the toilet bowl by means of a high-volume siphon. After the tank water has reached the toilet bowl, the additional water forces the contents of the bowl into the drainpipe for disposal. A siphon flush valve cannot leak because it has no rubber hardware to become worn over time.
Float ball fill valves are used to refill the toilet tank with water after flushing has occurred. This type of toilet valve consists of a hollow plastic ball attached to an automatic valve mechanism by a slender metal rod. The water level inside the tank drops when the flush valve is opened. The reduction in the water level causes the floating ball to lower and activate the valve mechanism. As new water enters the tank, the floating ball rises and shuts off the valve when the correct water level has been reached.
A float cup fill valve is a modernized version of a float ball toilet valve. In this toilet valve configuration, a hollow plastic cup is attached to the fill valve by a short plastic lever. This floating cup glides along the shaft of the fill valve as it rises and falls in response to the changing water level in the tank. Float cups open and close the fill valve in the same manner as a float ball but take up less space inside of the toilet tank. A float cup fill valve usually makes less noise when refilling the tank.