Abstract: The formation of bacteria and germs, in particular of legionella during the heating of hot water is prevented by the special cold water outlet inside the hot water heater. In this hot water heater the entire cold water consumption is directed through the hot water heater. At the same time the pressure level in the cold water system and in the hot water system is also the same, whereby the disadvantage of fluctuating mixing temperatures for the consumer is avoided, i.e. at the point of use.