A system includes rigid reservoirs, each divided by a flexible diaphragm into a hydraulic chamber and a delivery chamber. The hydraulic chamber is connected to a hydraulic liquid conduit via a valve and the delivery chamber is connected to a delivery conduit. A hydraulic actuator is operable to apply pressure to the hydraulic liquid so as to force the hydraulic liquid into a hydraulic chamber whose valve is open, pushing the diaphragm distally to force the delivery liquid from the delivery chamber into the connected delivery conduit. The actuator is also operable to apply suction to the hydraulic liquid in the hydraulic liquid conduit so as to draw hydraulic liquid from the hydraulic chamber, proximally pulling the flexible diaphragm to draw the delivery liquid from the delivery conduit into the delivery chamber.