Abstract: A tool for transferring controlled amounts of fluid into and from a fluid flow circuit is disclosed herein. The tool includes a substantially closed tube having a first end, a second end, and a chamber therein; an elongate plunger having a fore end extending inside the chamber and toward the second end of the tube, an aft end extending outside the chamber and from the first end of the tube, a piston-like structure on the fore end, and a manipulable structure on the aft end; a fluid inlet duct mounted on the tube; a first coupler mounted on the fluid inlet duct for connecting the duct with the fluid flow circuit; a fluid outlet duct mounted on the second end of the tube; a second coupler mounted on the fluid outlet duct for connecting the duct with the fluid flow circuit; and a fluid transfer duct mounted on the tube.