A device (10,110) for expressing liquids, comprising: a support structure having at least two separate compartments (11,12;111,112) for containing respective liquids; a distal wall (21,121) traversing the support structure proximate a distal end thereof; a duct extending through the distal wall enabling liquid to exit the at least two compartments; at least one plunger (16;116a,116b) movably affixed to the support structure proximate a proximal end thereof for infusing liquids from the device through the duct upon activation of the at least one plunger; and a closure plug removably attached to the support structure at the distal end thereof for connecting with a liquid-receiving device, the closure plug having a transverse resealable membrane with a selectively openable through passage allowing passage of liquids from the duct therethrough to enter the liquid-receiving device, wherein the closure plug is initially affixed within a plug-containing cavity at the distal end of the support structure by frangible sections, and the closure plug has a connection section to remain mechanically secured to the liquid-receiving device upon connection therewith, and the frangible sections are adapted to be broken to permit removal of the closure plug from the support structure upon completion of maintenance treatment of the liquid-receiving device when the device is removed from the liquid-receiving device, wherein the frangible sections are frangible tabs, which lie between an internal wall of the plug-containing cavity and an outside of the closure plug and which are adapted to be broken with a rotary motion of the support structure with respect to the closure plug. a support structure having at least two separate compartments (11,12;111,112) for containing respective liquids; a distal wall (21,121) traversing the support structure proximate a distal end thereof; a duct extending through the distal wall enabling liquid to exit the at least two compartments; at least one plunger (16;116a,116b) movably affixed to the support structure proximate a proximal end thereof for infusing liquids from the device through the duct upon activation of the at least one plunger; and a closure plug removably attached to the support structure at the distal end thereof for connecting with a liquid-receiving device, the closure plug having a transverse resealable membrane with a selectively openable through passage allowing passage of liquids from the duct therethrough to enter the liquid-receiving device, wherein the closure plug is initially affixed within a plug-containing cavity at the distal end of the support structure by frangible sections, and the closure plug has a connection section to remain mechanically secured to the liquid-receiving device upon connection therewith, and the frangible sections are adapted to be broken to permit removal of the closure plug from the support structure upon completion of maintenance treatment of the liquid-receiving device when the device is removed from the liquid-receiving device, wherein the frangible sections are frangible tabs, which lie between an internal wall of the plug-containing cavity and an outside of the closure plug and which are adapted to be broken with a rotary motion of the support structure with respect to the closure plug.