Two common types of check valves are ball cone valves and swing check valves. A ball cone valve utilizes a spring-loaded ball seated against a cone-shaped interior surface to stop the flow of fluid in a forward direction, and a swing check valve has a movable disc on a hinge to block reverse flow.
Check valves are rated by their cracking pressure (the minimum upstream pressure required for the valve to operate), and they are used on various bead filters for koi ponds
Valueble to protect your equipment. In aquaculture air pumps are often below the water line. Use these Valterra check valves to keep water out of the pump with minimum head loss. Ask for specs. Made in the USA by Valterra.