The primary purpose of an air injection check valve is to control the unidirectional flow of air in a given system, preventing backflow of air. This valve design allows gas to pass in one direction only and prevents flow in the opposite direction.
If a check valve is leaking, clogged, rattling, or deteriorating, i.e., gas is able to flow backward through the valve, this is an indication that the sealing performance of the valve has been degraded, possibly due to a worn out spool, spring failure, or a damaged seat. Replacement is then required to restore the system to normal operating condition.