Abstract: A thermostatically controlled mixer battery. The appropriate mixer battery having plate control means 2 comprising at least one rotatable control plate 24 for controlling the quantity of water delivered and manually actuable from externally by a user, the plate 24 having bores 243, 244 selectively alignable with hot and cold water inlet bores 233, 234 and a temperature control plate 25, which is thermostatically actuated and is sealingly displaceable relative to the quantity control plate 24, the plate 25 having bores 253, 254 formed therein which permit the hot and cold water to pass therethrough in a desired ratio to a mixing chamber 15.