A control system for one or more ablutionary devices includes a mixer valve having a first inlet and a second inlet configured to receive a supply of hot and cold water, and an outlet configured to output cold water, hot water or a mixture thereof as an output stream for suppling water to the one or more ablutionary devices downstream of the mixer valve; and a controller in communication with the mixer valve. The controller is configured to obtain a supply coupling setting that indicates which of the first and second inlets is to receive, or is receiving, hot water during operation of the control system and which of the first and second inlets is to receive, or is receiving, cold water during operation of the control system; and control the mixer valve according to one or more target output water properties and the supply coupling setting.