One of the concerns with storing hot water at a high enough temperature to kill Legionella bacteria is that it creates a risk for scalding. There is always a balancing act between hot water storage temperatures that prevent Legionella bacteria growth and scalding concerns. Plumbing engineers have recommended hot water storage temperatures in excess of 135 to 140 degrees Fahrenheit to minimize Legionella bacteria growth and they recommend using a master thermostatic mixing valve to mix cold water with the hot water and deliver hot water at 120 degrees or less to minimize the risk of scalding.