Valves are devices to that are used to regulate the flow of fluids and gases by obstructing them or allowing them to pass through pipes or cisterns. There are various types of valves, each for a specific operation and use.
A check valve is a valve in which liquids are allowed to flow in a single direction. These valves are used in situations where the direction of liquid flow must not be allowed to reverse itself. These have tremendous usage in municipal water systems where polluted water is prevented from flowing back into the drinking water supply.
Check valves are also known as one-way directional valves. Because they have a fast reaction to flow reversals and they possess instant shut-off characteristics, you can perform maintenance down the line without losing all of the pressure in the system.
The way that the most common type of check valve (ball check valve) works is quite basic as a ball with a larger diameter than the hole in the valve seat either floats freely or is spring-loaded. This enables the liquid to flow, however if the flow is reversed, the ball will be pushed back against the hole in the seat and will totally block it and stop any backwash from getting into the system.
Although ball check valves are the most common type of check valves other types are used in certain situations. Cone check valves are similar to ball check valves except the actuator is cone shaped instead of spherical. Lift check valves use a disk as the actuator and if the disk put into its place by a spring, it can be used in any type of directional mounting.
Other common check valves include clapper valves and double check valves. A double check valve is often used to prevent liquids from flowing back. Clapper valves are normally used in firefighting equipment. These types of valves are also widely used widely in irrigation equipment. Because of the different types of check valves available you need to make sure that you select the right check valve for the job that you are doing.