Abstract: A device for separating liquids of lower density than water, in particular oil, from water, comprises a pump and a separator receiving the liquids from the pump. The separator comprises a settling chamber and a filter pack arranged behind the latter. A line between the pump and the settling chamber feeds the liquids exclusively to the latter. The line includes a vent valve. An overflow opening device is provided between the settling chamber and the filter pack. A shut-off member is provided for closing the overflow opening in response to the thickness of the layer of liquid of lower density collected in the settling chamber.