A mixing valve combines hot and cold water to produce a safe temperature. Thermostatic mixing valves are used as safety devices to control hot water temperature and prevent scalding. Water stored at high temperatures can cause thermal shock, so the maximum safe temperature for domestic systems is 122°F. Thermostatic mixing valves have a central thermostat unit and prevent scalding in the event of a cold water supply failure. Manual mixing valve faucets are popular but offer no protection against scalding, so at least one thermostatic mixing valve is required in all hot water systems.
A mixing valve is a fairly general term used to describe many devices that combine hot and cold water to produce a comfortable and safe temperature. It is most commonly used to describe thermostatic mixing valves fitted as scalding safety devices in hot water systems. These safety valves automatically control the hot water temperature and can be centrally located to control flow to all outlets or installed at individual points of use. The term mixing valve can also apply to single spout, hand mixer taps in sinks, bathtubs and showers. These valves have a wider adjustment range but by themselves offer no protection against scalding and thermal shock.
It is becoming common practice to keep water stored for domestic applications at high temperatures to prevent the development of dangerous bacterial strains. Typically these temperatures exceed 140° Fahrenheit (60° Celsius), which is hot enough to cause severe sunburn and thermal shock. It is generally accepted that the maximum safe temperature for water used in domestic systems should not exceed 122° Fahrenheit (48° Celsius). In many areas it is mandated that hot water system outlets be set no higher than 122 degrees. For this reason centralized thermostatic mixing valves may be required by law for new hot water systems.
Thermostatic mixing valves are equipped with a central thermostat unit which is pre-set to the desired flow temperature. The valve housing has hot and cold inlets and a mixed water outlet. The thermostat mechanism is mechanically linked to a mobile piston which regulates the amount of hot water it puts into the valve according to the outlet temperature. If the cold water pressure drops significantly or is switched off, the valve will immediately cut off the hot water supply. This prevents any possibility of scalding the end users in the event of a cold water supply failure.
A single central thermostatic mixing valve is the most common installation arrangement, although several point-of-use faucets that feature thermostatic control are available. Typically, however, a single unit is installed on the main outlet of the water heater which then feeds water below 122° to the hand mixers in baths and showers. This allows the user to preset the flow temperature to their liking without any fear of a sudden surge in dangerously hot water.
Manual mixing valve faucets are still, however, very popular in kitchens and bathrooms. These devices contain the same internal arrangement and mechanisms as a thermostatic mixing valve with the exception of manual adjustment. Hand mixers can consist of dual tap controls or single one-way controls with a single spout or outlet for mixed water. While generally a very attractive decorative addition, a hand mixer valve by itself offers no protection against sudden drops or interruptions in the cold water supply. To avoid the possibility of scalding, at least one thermostatic mixing valve must be installed on all hot water systems.
Protect your devices with Threat Protection by NordVPN
