The National Research Council (NRC) Standing Committee on Building and Plumbing Services recently adopted a change to the Plumbing Code that requires water supplied by fittings in residential buildings to be limited to a maximum of 49° C (120° F).
This change will be adopted only for new construction. However, it does not set the accepted best practice for water temperature control for all water heater installations. The higher the water temperature the shorter the time taken to scald. Water stored at 49° C (120° F) or less can provide ideal conditions for the growth of legionella bacteria within the water heater.