Apparatus and method for detecting and recovering immiscible liquids of different densities

In a sump having varying surface fluid levels, a method for detecting a first fluid layer of a first fluid of given specific density gathered from an interface with a second fluid having a higher specific density, comprising the steps of:

• providing a recovery unit for floating within the sump at the varying surface fluid levels having a specific gravity greater than the given specific density but less than the higher specific density whereby the recovery unit floats on the second fluid having the higher specific density at the interface between the first fluid layer and the second fluid layer;
• floating said recovery unit on the surface of the sump;
• providing means on the recovery unit for receiving fluid from the first fluid layer;
• providing an air source;
• providing a bubbler hole defined within the recovery unit for discharging air within the recovery unit at least below a surface of the first fluid accumulated within the recovery unit;
• communicating air from the air source to the recovery unit at the bubbler hole for discharging air from the bubbler hole through at least a portion of the first fluid layer;
• measuring back pressure in the conduit between the air source and bubbler hole to determine thickness of the first fluid layer above the bubbler hole;
• and,
• pumping the first fluid from the recovery unit responsive to the measuring of back pressure in the conduit.