Abstract: An apparatus is disclosed for cleaning the movable parts of a displacement-type liquid level sensor while the sensor is maintained in continuous service. Alternatively, the sensor may be isolated from the process and cleaned without disassembly. In either use a cleaning fluid is introduced to the housing of the sensor containing the movable parts. The flow of the fluid flushes solid particles off of and away from the movable parts of sensor, thus providing reliable operation for measuring the level of chemical liquids such as Phosam solution (diammonium phosphate), that are likely to form solid materials during processing or storage.