On a two-way or three-way valve, turn off all incoming air, disconnect pipe/hose from the work port and plug it. Turn the air back on. If the valve continues to leak it should be removed from service and repaired or replaced.
If the valve is a 4-way or 5-way leave the air on. Whichever work port is exhausted remove hose, pipe or tubing. Determine if the leaking air is coming out of the valve or the ‘work.’ Reinstall piping and cycle valve. Remove the other hose, pipe, or tubing and repeat steps. If the leaking air is coming out of the valve remove the valve from service and repair or replace.
If the leak is coming out from the work (cylinder, actuator, air motor, etc.) the system should be shut down and the work should be serviced or replaced.
