Abstract: Apparatus is provided to supply a liquid, for example water, at a constant temperature, for example to a shower by mixing two supplies of the liquid, one hot and the other cold. Control of the output temperature is effected by measuring and controlling the flow rate in one or both of the supplies by way of flow meters having a rapid response time and motor driven valves.In the case where the flow rates in both supplies are measured and controlled it is possible further to control the output flow rate in addition to and independently from the output temperature, also by controlling the flow rates in the supplies.Further accuracy may be achieved by sensing the input supply temperatures in addition to the flow rates.