Thermostatic mixing valve
A thermostatic mixing valve (TMV) is a valve that blends hot water with cold water to ensure constant, safe shower and bath outlet temperatures, preventing scalding. The storage of water at high temperature removes one possible breeding ground for Legionella; the use of a thermostat, rather than a static mixing valve, provides increased safety against scalding, and increased user comfort, because the hot-water temperature remains constant. Many TMVs use a wax thermostat for regulation. They also shut off rapidly in the event of a hot or cold supply failure to prevent scalding or thermal shock. It  is increasingly common practice around the world to regulate the storage water temperature to above , and to circulate or distribute water at a temperature less than . Water above these temperatures can cause scald injuries. Many countries, states, or municipalities now require that the temperature of all bath water in newly built and extensively refurbished domestic properties be controlled to a maximum of . Installing thermostatic mixing valves can ensure that water is delivered at the required temperature, thereby reducing the risk of scalding accidents; it also reduces hot water consumption from a supply that is maintained at a higher temperature. There  are three main categories for water temperature controlling devices: Heat Source, Group Control, and Point-of-Use. These are used with central heating systems that use water as a medium. These provide a uniform distribution temperature for all hot water outlets in a household. These are single Outlet Thermostatic Mixing Valves, often called "thermostatic faucets", "thermostat taps" or "thermostat valves". Although other temperature regulating valves exist, thermostatic mixing valves are the preferred type in health care facilities, as they limit maximum outlet temperature, regardless of pressure or flow.