Prevention of hot tap water burns--a comparative study of three types of automatic mixing valve

To prevent fatal outbreaks of Legionnaires' disease, particularly in hospitals and other health-care premises, building services engineers are recommended to store and operate hot water systems at a temperature of 60 degrees C. However, water at this temperature can cause serious scalding. It is therefore advised that mixing valves be installed in the hot water supply pipework to provide hot water at safe temperatures for washing and bathing. Electricity Association Technology Ltd (EATL) investigated the performance of three makes of automatic mixing valve. Tests showed that with constant supply conditions there was little difference in performance between the three valves when blending hot and cold water. However, the ability of the valves to respond to the loss of the cold water supply was quite valve was able, consistently, to shut the hot water off in the event of cold water failure. These results suggest that where it is necessary to safeguard people or patients against any risk of scalding, e.g. young children and handicapped patients, a quality thermostatic valve should be installed rather than a cheaper tempering valve.