The optimal temperature setting against legionella in hot water

The concern about Legionella in drinking water is certainly justified. With a suitable temperature setting or alternatives to the hot water preparation technology, the risk of infection by the rod bacteria can be reliably eliminated. We'll show you what options you have.

What hot water temperature is required against legionella?

Legionella are rod bacteria and can cause the lung disease legionellosis in humans. Many therefore worry about the harmlessness of their drinking water from the domestic tap. Legionnaires' disease is not a trivial matter and, if left untreated, can even be fatal. The risk of developing it is, however, linked to a number of influencing factors and overall, according to the prevalence statistics, not particularly high. The following conditions are causative for infections:

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  • Increased colony formation in water between 25 and 50 ° C
  • Insufficient / non-existent water circulation in the pipe system
  • Bacteria get into deep lungs by inhaling steam
  • Possibly. Susceptibility to chronic smoking or renal insufficiency

First of all, as is the case with all infectious diseases, people with a weak immune system and those who are sensitive to the disease are particularly at risk. Of course, people with healthy lungs and a strong immune system need to worry less than people with damaged lungs and generally poor health.

Nevertheless, it is always extremely useful not to give legionella the opportunity to multiply in the drinking water heating system in the first place. A few simple measures are sufficient for this.

Sufficient temperature

In existing drinking water heating systems with hot water storage tanks, the setting of a minimum temperature serves to kill legionella. A temperature range of 30 to 45 ° C is ideal for the bacteria to multiply. It is no longer possible to continue at a temperature of 55 ° C. Set the target temperature of the drinking water storage tank to this minimum temperature.


A circulation pipe system with direct return lines is mandatory in Germany from a certain pipe content up to the tapping point furthest away from the water heater. The circulation pump does not have to be switched on all the time, after all, it also consumes valuable energy and too much circulation also causes heat losses. Nevertheless: Legionella cannot multiply in a hot water system that is kept constantly in motion.

Fresh water heating

An alternative is to always have the hot water heated up on demand instead of a drinking water storage tank - for example with instantaneous water heaters or gas boilers. The risk of legionella multiplication is thereby set to zero because the drinking water does not stop longer in a reservoir.

Sanitary storage

If you do not want to install fresh hot water processors at all the tapping points in the house and want to stick to the central storage system, you can also use a hygienic combination storage tank for the heating and warm drinking water instead of a separate drinking water tank. The hot water for the drinking water pipe is also heated in this using the continuous heating principle.