Check valves are used to prevent backflow of media. They open automatically using the fluid's own kinetic energy and automatically close when reverse flow occurs. Check valves come in three types: swing, lift, and wafer. Swing check valves only allow fluid to flow from left to right, automatically closing in the reverse direction. Lift check valves lift the valve core when fluid flows from left to right, creating a passage. Reverse flow compresses the valve core against the valve seat, closing the valve. Wafer check valves open the valve core when fluid flows from left to right, creating a passage. Reverse flow compresses the valve core against the valve seat, closing the valve. Wafer check valves can be installed in multiple positions and are compact, lightweight, and compact.

They are commonly found at pump outlets, steam trap outlets, and other locations where reverse flow is prohibited.