Hygienic valves used for flushing are normally a flap or siphon type mechanism.
Most residential toilets use one type of valve to flush and another type to fill the tank. Discharge valves must be activated manually, while filling valves open and close automatically. There are only two basic types of valve mechanisms for each of these operations. Hygienic valves used for flushing are normally a flap or siphon type mechanism. Fill valves are usually activated by a ball or float cup device.
A flush valve usually allows water to pass from the cistern into the basin.
Flapper style toilet valves are usually made of rubber and fit into a large opening at the bottom of the tank. This valve is attached to the toilet flush handle by a chain. When the toilet handle is pressed, the chain opens the flap valve and allows the water from the tank to enter the toilet at high speed and flush the contents of the toilet. Flapper style sanitary valves are the most commonly used type of flushing mechanism. These valves have a tendency to deform over time and leak.
Siphon-type sanitary valves have been used for over a century in residential toilets. When the flush handle is pressed in this type of flushing mechanism, water from the tank enters the toilet via a high volume siphon. After the water from the tank reaches the toilet, the additional water forces the contents of the toilet into the sewer pipe for disposal. A siphon flush valve cannot leak because it has no rubber parts to wear out over time.
Floating ball fill valves are used to refill the toilet tank with water after flushing. This type of sanitary valve consists of a hollow plastic ball attached to an automatic valve mechanism by a thin metal rod. The water level inside the tank drops when the discharge valve is opened. Reducing 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 closes the valve when the correct water level is reached.
A floating cup filling valve is a modernized version of a floating ball sanitary valve. In this toilet valve configuration, a hollow plastic cup is attached to the fill valve by a small plastic lever. This floating cup slides along the axis of the fill valve as it rises and falls in response to changing water level in the tank. Floating cups open and close the fill valve in the same way as a floating ball, but take up less space inside the toilet tank. A floating cup fill valve generally makes less noise when refilling the tank.