One Way Check Valve

A check valve, also known as a non-return valve or one-way valve, is used in hydraulic systems to prevent the reverse flow of oil and in pneumatic systems to prevent the reverse flow of compressed air.
The function of a check valve is to allow fluid to flow in one direction while preventing it from flowing in the opposite direction. When the fluid passes through the valve body, the pressure opens the valve. Any fluid flowing in the opposite direction will close the valve. The valve is closed by the weight of the check mechanism, back pressure, or a spring.