The KK-5020 is the Pressure Relief Kit that screws to the side of the ON/OFF Pressure switch. This KK-5020 relief valve is designed to release the built up pressure in the air compressor pump head and lines after the air compressor reaches the maximum pressure allowed by the pressure switch.
Many times the KK-5020 Pressure Relief or the Pressure Switch is replaced because the air will continue to leak out of the relief valve continuously until the air compressor tank is empty. If this is the problem you are having then the KK-5020 pressure relief valve is working properly and most likely not you problem.
The Pressures Relief Valve is designed to release the built up pressure in the air compressor pump head and lines and after the air compressor reaches the maximum pressure allowed by the pressure switch and turns off.
When this happens and your air compressor is working properly you will hear air release from the pressure relief valve for 3 to 5 seconds and slowly stop.
When the air continues to leak from the pressure relief valve then you will need to look at the one way check valve that is in you air compressor tank.
The Check Valve allows pressure to go from your air compressor pump directly into the air compressor tank. When this valve is operating properly the air can only go into the tank and is then prevented from coming back out of the tank by the "One Way Check valve".
When this valve is defective, damaged or worn the air will then escape from the compressor tank and travel back past the one way check valve, this air will now look for a place to escape and will typically leak out from the pressure relief valve located on your On /Off pressure switch.
The check valve is located at the end of the main outlet line that come off of the air compressor pump and goes into your air compressor tank. Remove this line from the air compressor pump and the air compressor tank and you will then be able to access your check valve to replace you check valve.