Abstract: A water coolant circuit for a dental unit includes a plurality of defined dental device positions to which dental devices that use water coolant can be connected and a water coolant valve connected to the plurality of dental device positions and connectible to a pressurized water coolant source. The water coolant valve is operable via pulse width modulation (PWM) and selectively controllable to supply the water coolant from the water coolant source to at least one of the plurality of dental device positions at a time. The water coolant valve used for the plurality of dental device positions can have an associated water holdback valve for each of the dental device positions. A new proportional air coolant valve is described.