A drainage device for placement on a housing includes an external plug component and a liquid expandable component. The external plug component has a first cap section and a second attachment section. The first cap section is positionable over an exterior side of a housing wall. The first attachment section is adapted to attach the drainage device to an opening in the housing wall. The liquid expandable component contacts the external plug component and is adapted to contact a structure within the housing when the drainage device is placed on the housing. Characteristically, the liquid expandable component has a higher volume when contacted with liquid than when dry. The liquid expandable component pushes the internal plug component away from the structure within the housing when the liquid expandable component transitions from a non-liquid-containing state to a liquid containing state thereby providing a path for liquid to escape.