What is the ideal temperature for domestic Hot Water

People often ask me: “What is the temperature of the domestic hot water?” If you read the model codes, it indicates that the maximum hot water temperature for a shower or bathtub is 120 degrees Fahrenheit. If you read the warning labels on the side of most water heaters, the maximum hot water temperature is 120 degrees Fahrenheit on some labels and 125 degrees Fahrenheit on the other labels. The 125 degree limit probably allows some temperature loss before the hot water reaches the fixtures. Most documents on water heaters and warning labels mention the availability of thermostatic mixing valves or automatic temperature compensators and recommend their use. If you look at several of the industry standards for shower mixers, they indicate that faucets must have adjustable stops to limit the maximum hot water temperature to 120 degrees Fahrenheit. The tests provided for in the standards provide test criteria for testing shower valves to these limits.