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One can practice both safety and economy by keeping water temperature at doctor approved levels. Very hot water temperature can cause burns with great rapidity, and as such, care in setting your hot water heater is required. Setting the hot water temperature lower also means a savings in energy bills for heating the home's water in many cases. However, a lower temperature does mean you will run out of hot water more quickly.
Most experts recommend that hot water temperature should not exceed 125° F (51.66° C). A water temperature exceeding this poses serious risk of bad burns, particularly to children. In fact even at 125° F, if the child puts his or her hand in the water continuously for two minutes he or she may get second or third degree burns.
Some pediatricians instead suggest setting the hot water temperature at 120° F (48.88° C). With this water temperature, a child would have to run water over the same place for ten minutes prior to receiving a severe burn.
Temperatures higher than 125° F can burn a child, or an adult quite severely, and quite quickly. For example, it is estimated that it takes only two seconds of exposure to water at 150° F (65.55° C) and only six seconds of exposure to water at 140° F (60° C) to cause a very bad burn to a child.
Some are concerned that lowering the water temperature will result in soap working improperly in dishwashers or washing machines. Actually most soap and detergent is meant to work at between 120° to 125° F. Thus soap is actually designed for this temperature.
Others are concerned that lowering water temperature might lead to greater chances of passing illness between family members. Actually, the best method for preventing illnesses is handwashing with warm, not hot, soapy water. 120° F water is quite hot enough to wash most germs away. It will not always work, since some germs are airborne and one contracts them through exposure or inhalation of the infected droplets of someone else, as after a sneeze.
In terms of cost saving, dropping the water temperature setting by ten degrees typically saves approximately 4% on one’s cost to heat water each year. This can make a profound difference if dropping the water temperature from 150° to 120° F, saving essentially 12% a year.