Check valves

A check valve is a device that only allows the flow of fluids in one direction. They have two ports, one as an inlet for the media and one as the output for the media. Since they only allow media flow in one direction, they are commonly referred to as ‘one way valves’ or ‘non return valves.’ The main purpose of a check valve is to prevent backflow in the system. Figure 1 shows an example of a check valve.

A check valve relies on a pressure differential to work. They require a higher pressure on the input side of the valve than the output side to open the valve. When the pressure is higher on the outlet side (or the input side pressure is not high enough), the valve will close. Depending on the valve type, the closure mechanism is different. Unlike other valves, they do not need a handle, lever, actuator, or human to correctly work.