Check valves, also known as non-return valves, ensure media travels through a system in the intended direction and prevent backflow. Flowing media pushes the disc away from the seat, opening the valve and backflow pushes the disc back into place and closing the valve. Swing check valves are used for high-flow applications, viscous substances, and fluids containing suspended solids. Ball check valves are compact and suited for high-pressure applications and viscous media. Piston check valves are used for low-flow applications and low-viscosity media. Poppet check valves suit low-pressure applications, such as hydraulic systems. Diaphragm check valves use flexible diaphragms to prevent backflow. Food grade and sanitary air blow check valves evacuate residual media from lines, maintaining conditions and preventing corrosion. Foot valves install at the end of a pump's suction line to prevent back-siphonage when the pump is off.