In one example in accordance with the present disclosure, a fluid extraction system is described. The fluid extraction system includes an interface to fluidically and electrically couple a removable extraction reservoir to a printing device. A return line of the fluid extraction system is to connect the interface and a reservoir of the printing device. The fluid extraction system includes a switch to 1) responsive to attachment of the removable extraction reservoir to the printing device, open the return line to direct fluid form the reservoir to the interface and 2) responsive to removal of the removable extraction reservoir from the printing device, close the return line.