This is an authentic replacement part manufactured for use with DeWalt air compressors. The check valve is used to allow air to flow from the pump to the tank and prevents air from escaping the tank and returning to the pump. A faulty check valve will allow the compressor to function as normal, then the pump will attempt to turn on but th...Read moree motor will only produce a humming noise. When the motor can potentially overload if a worn check valve does not allow the pump to engage. This check valve is available as an individual replacement part.