A device for drainage includes a tubular reservoir having a tubular pliable wall, a rigid cover, and a rigid bottom, and also includes at least one spring which applies a force that presses the cover and the bottom apart, wherein the cover is movable in the direction of the bottom in order to place the spring into a start position. One or more magnets are configured such that the magnets apply an additional force on the reservoir in such a way that a resulting force pressing the cover and the bottom apart is substantially constant across as the spring is deflected.
