An aspirator-ejector apparatus adapted to aspirate one fluid and supply another fluid without mixing them and comprising an aspiration tube adapted for connection to a vacuum source, and a supply tube adapted for connection to a reservoir of supply fluid. A closure valve for the aspiration tube normally interrupts communication between the aspiration tube and the vacuum source, and a closure valve for the supply tube normally interrupts communication between the supply tube and the reservoir. At least one control member serves for opening both closure valves, and a pump is connected to the tubes to pump fluid from the reservoir to the supply conduit. The pump comprises a flexible, sealed member defining first and second distinct chambers, the first chamber being connected to the vacuum source, the aspiration tube and the corresponding closure valve, the second chamber being connected to the supply tube, the reservoir and the corresponding closure valve.