Abstract: In a centrifuge for the separation of solids from liquid in which concentrated solids are discharged from radial nozzles at the periphery, there is provided an concentrated solids underflow discharge control apparatus which senses an increased concentration of solids in the underflow and adjusts the flow of the recycle stream as a result thereof to prevent solids from spilling over into the effluent overflow. A sensing chamber and a control module having a flow interference device is utilized to measure a set level backup. Any alteration of said level is detected by a level sensor which sends a signal to a level indicator control and in turn controls the opening and closing of a recycle line valve which controls underflow.