A device for capping and sealing a refrigeration service valve fitting of quick disconnect type for minimizing unwanted seepage of refrigerant from the fitting. The device includes a cap defining a base and an open-ended sealing portion extending longitudinally from the base. The sealing portion defines first and second internal cylindrical surfaces wherein the first surface defines a first internal diameter and the second surface defines a second internal diameter greater than the first diameter and wherein a shoulder defines a boundary between the surfaces. The first surface defines a groove containing an annular flexible member for sealingly engaging the fitting when the device is positioned on the fitting. Features are provided in relationship with the sealing portions for removably retaining the device on the fitting by engaging a conventional lock groove in the fitting.