Cloacina uses tracer dye tests to enable visual observation of flow as it travels through a wastewater treatment plant. Tracer dye tests verify sufficient mixing of process flow and verify hydraulic retention time (HRT) - the average time a particle of water spends in a tank or in the system at a given flow rate. During the test, a fluorescent yellow-green liquid dye is injected into clear, flowing water at the head of a plant to check for any "dead spots" in a process tank - areas where clear water is not mixed with or displaced by dyed water.