Abstract: Device for filtration of liquid medium, having a filter housing (2) with a filtration chamber (3) delineated by a base element (10) and a cover (20). A drain duct (15) in the base element to drain medium from the filtration chamber. A filter cassette (30) fitted detachably in the filtration chamber. The filter cassette has a first endwall (31) towards the cover, a second endwall (32) towards the base element, and a filter element (33) fastened to, and extending between, the endwalls. The endwalls and the filter element together delineate an internal space (34) for a medium to be filtered. The filter cassette has a drain tube (40) which protrudes from the second endwall and has its inner end leading into the internal space of the filter cassette. The drain tube is accommodated in the drain duct when the filter cassette is fitted in the filtration chamber.