The onset of drainage of liquids from plastic tubes was evaluated. One end of the tubes was plugged, filled with liquid, oriented horizontally, and attached to a rotor. With their open end facing outward, the filled tubes were spun at progressively higher speeds until they began to drain. Resistance to drainage was independent of the tube length, but depended on the surface tension and density of the liquids as well as the diameter and wettability of the tubing. We found that the onset of drainage could be explained in terms of a critical centrifugal acceleration.