A thoracic cavity drainage device includes a first vessel having a plurality of chambers one of which is a regulated drainage chamber, and a separate transfer vessel which receives fluid collected in the drainage chamber of the first vessel. The chambers of both vessels are interconnected in a series by fluid passageways which cooperate to maintain a uniform range of suction in the drainage chamber while preventing passage of water into the drainage chamber and permitting a different level of suction in the transfer vessel. This operation is effective despite relatively large pressure and vacuum impulses caused by stripping of drainage lines, patient coughing, and the like, and despite discrete changes in the physical configuration of the system caused by disconnection of the transfer vessel, connection of the transfer vessel to an infusion line or the opening or closing of fluid lines and ports. A novel transfer vessel empties the drainage device and provides gravity reinfusion of the collected fluids. A mechanism within the transfer vessel provides an effective suction without vacuum connections or pressure regulating adjustments.