Abstract: A dental unit water line (DUWL) monitoring and maintenance apparatus, for monitoring a DUWL. The apparatus has a cleansing unit attached to the DUWL for cleansing the fluid passing there through. A control unit controls the cleansing unit associated with the water line. A monitoring unit monitors the operation of the dental unit when used by a dentist and stores data related to that operation. A timer times and records data relating to both periods of dental unit activity and inactivity, wherein, in use, the control unit operates to receive data from the monitoring unit and the timer and, based upon that data and reference data controls the operation of the water line to control flow of fluid through that DUWL and controls the cleanser to control the overall cleansing procedures associated with both the dental unit and associated DUWL.