This European Standard specifies dimensions, materials and performance requirements (including methods of test) for in line hot water supply tempering valves for sanitary hot water systems, of nominal sizes from DN 15 to DN 50. Tempering valves reduce the temperature of sanitary hot water for distribution throughout the hot water system. The conditions of use are specified in Table 1. The valves are intended to be used with storage water heaters to provide tempered hot water to the terminal fitting. They are not intended to control the temperature at the point of use. Tempering valves control the distribution temperature from a water heater to a preset value or an adjustable range, both between 45 °C and 65 °C.