Leak was coming from the nut of the piston. I tightened down the nut to ensure that it was properly sealed. I added 4lbs of refrigerant to the system to satisfy factory charge. I advised the customer to have a pure air UV light installed inside the air handler. Customer agreed that he will have it installed but wants to wait until the spring time when he gets the next check up to move forward with the work. Please schedule work to be performed when the next tune up is scheduled.