How hot the water should be in your water heater should not be taken lightly. Every year in the US about 3,800 people are injured and 34 are killed by scalding injuries caused by hot water from the tap, the majority of them are people with handicaps, elderly and young children. Many of these are caused by domestic hot water coming out of the taps at temperatures higher than 120 degrees F which is the highest temperature setting recommended by the Consumer Product Safety Commission.
Scalding injuries can occur to adult skin in about 5 minutes with 120 degree F water, 30 seconds at 130 degrees F, 5 seconds at 140 degrees F, 1 Â½ seconds at 150 degrees F, and Â½ second at 160 degrees F. The severity of the burn depends on how far through the layers of skin the burn extends. With children and the elderly the layers of skin are thinner so the burns occur much more rapidly and are more severe even with shorter exposure times.
When water heater temperature settings are set higher than 120 degrees F for reasons such as increased hot water capacity, meeting higher temperature requirements for dishwashers in a restaurant, and bacteria control in the hot water system an appropriate mixer valve, tempering device, or, temperature limiting device must be installed to prevent water above 120 degrees F from coming out at taps where people may be scalded. These devices must meet the applicable standards such as ASSE 1016, ASSE 1017, ASSE 1069, & ASSE 1070 to ensure safety from scalding.