What is the minimum temperature that hot water should be delivered from a residential hot water heater?

The minimum temperature that hot water should be delivered from a residential hot water heater is 120 degrees Fahrenheit. This temperature is recommended by the U.S. Department of Energy and the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to reduce the risk of bacterial growth, particularly by preventing the formation of Legionella, a bacterium that can cause Legionnaires' disease.

At temperatures lower than 120 degrees, there is an increased risk of bacteria thriving in the water, which can pose health risks to occupants. Conversely, temperatures higher than 120 degrees can cause scalding, especially in young children or the elderly. Therefore, setting the hot water heater to 120 degrees strikes a balance between safety and effective water heating, ensuring that hot water is available while minimizing health hazards.

Understanding these guidelines is crucial for home inspectors, as it highlights the importance of ensuring that residential hot water systems are set to appropriate temperatures for both health and safety compliance.