Mixing Valves – What Are They and How Do They Work?

The American Society of Sanitary Engineering (ASSE) publishes a comprehensive set of industry standards that address various types of mixing valves intended for blending hot and cold water in domestic water systems. Each standard clearly defines the purpose, scope and application of a device that is manufactured and tested to perform for its application.

03/01/2007


The American Society of Sanitary Engineering (ASSE) publishes a comprehensive set of industry standards that address various types of mixing valves intended for blending hot and cold water in domestic water systems. Each standard clearly defines the purpose, scope and application of a device that is manufactured and tested to perform for its application.

ASSE 1017

ASSE 1017 is for master mixing valves that are located at the water heater. These valves mix hot water with cold water to deliver hot water that does not cause scald injuries. Master mixing valves often are placed at the water heater to store water at 140°F or higher, which limits Legionellae bacteria growth in the tank. The mixing valve then delivers hot water to the distribution system at approximately 120°F. In addition, an ASSE 1016 valve should be used downstream of this device to control thermal shock that may occur with changes in system pressure.

ASSE 1016

ASSE 1016 covers three types of valves: thermostatic (type T), pressure balancing (type P), and combination thermostatic and pressure balancing (type TP). The ASSE 1016 standard is for shower and combination tub/shower applications only, and developed for valves that control flow to 2.5 gallons per minute. The standard requires these valves to control temperature fluctuations caused by sudden pressure changes to within 3.6°F, which limits thermal shock.

P valves and T valves must react within one second of experiencing a pressure change to adjust water temperatures within 3.6°F. TP valves naturally control pressure and temperature fluctuations.

The standard also calls for a temperature limit stop at 120°F. Most manufactures ship their valves without setting limit stops, but include instructions on how it should be done.

ASSE 1070

ASSE 1070 is a standard for local mixing valves to limit hot water temperatures to 120°F. The valves are thermostatic mixing valves intended to be used near the point of use. Common applications include limiting temperatures for bathtub fill faucets and shampoo bowls; delivering tempered water to lavatories with or without infrared or metering faucets; and limiting hot water temperature to a specific side of faucets and fixtures.

ASSE 1069

The ASSE 1069 standard has a tighter temperature tolerance for master mixing valves than what ASSE 1017 requires. This valve delivers tempered water to serve showers in prisons, schools, health clubs and similar shower rooms that utilize push button metering valves or on/off valves in a single temperature shower system.

ASSE 1071

ASSE 1071 requires the valve to monitor outlet temperature and bypass cold water in the event of an over-temperature situation. This is the only type of valve approved for emergency shower and eyewash installations.



Scalding and Thermal Shock

• Scalding occurs when skin is severely burned.

• Scalding is caused when skin is in contact with temperatures in excess of 120°F. With each increase in temperature, the time it takes to receive a serious injury is reduced.

• Thermal shock occurs from a sudden change in water temperature and pressure.

• Thermal shock may lead to slip and fall injuries.



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