Abstract: An apparatus for separate drainage of two non-miscible liquids, especially oil and water, from a surface, especially from the deck (4) of a tanker (1). The apparatus comprises an upwardly open, well-forming container (11) which, in use, is installed with its upper edge essentially flush with said surface (4), and which is provided in its upper portion with a first (13) and a second (14) outlet means, the first outlet means (13) being located at a lower level than the second one (14). In the container (11) there is provided an inner tube (15) having a lower open end at the bottom (12) of the container (11), and an upper end which is carried in a sealing manner through the wall of the container (11) and is connected to the first outlet means (13).