Abstract: A method for monitoring and controlling water quality in a water phase changing device, such as an ice maker, having a water inlet, a water outlet, a reservoir configured for retaining a supply of water and being in fluid communication with the inlet and the outlet, and a flow controller for controlling the flow of water into the device, such as an ice maker, includes the steps of monitoring TDS concentration of water retained in said reservoir, and actuating at least one of a water input controller and a water dump controller to adjust the composition of the water in the reservoir when the monitored TDS concentration exceeds a preset TDS target concentration.