Tempering valves blend hot and cold water to deliver mixed water at a constant temperature.
They incorporate a temperature sensitive element which expands and contracts depending on the temperature of the water flowing across it. This action of the element in turn moves a piston which shuttles between the hot and cold ports. In doing so the valve maintains an essentially constant outlet temperature, and thus reduces the risk of scalding accidents.
This is an adjustable valve and the temperature range is between 38 and 65 degrees celsius.