Legionella in hot water: what Tyrol recommends

The federal state of Tyrol provided information about legionella on 7 October 2026 and gave households two clear temperature values: the central hot water cylinder should be set to at least 60 °C, and at least 50 °C should be reached at the tap after running it briefly. For you as a heat pump owner, this is important because it prepares hot water most efficiently at lower temperatures. Both can be reconciled if the system is set up correctly.

Why temperature matters

Legionella are bacteria that occur naturally in water almost everywhere. They become a problem when they multiply rapidly in pipes and cylinders. According to the federal state of Tyrol, this happens mainly between 25 and 45 °C and where water stands for a long time. They are only reliably killed off at temperatures of 60 °C and above.

You do not get infected by drinking the water, but by inhaling fine droplets, typically while showering. Most infections do not cause any symptoms. However, in older people, those with a weakened immune system, and people with chronic lung diseases, it can lead to pneumonia. According to the federal state, there have already been cases this year too.

What this means for the heat pump

A heat pump works more efficiently the lower the temperature it has to deliver. Every additional degree in the cylinder increases the amount of electricity used. klimaaktiv therefore recommends not setting the cylinder above 55 °C during normal operation. To ensure that no germs can survive, modern cylinders heat the water to a significantly higher temperature at regular intervals, according to klimaaktiv to around 70 °C.

The Energieinstitut Vorarlberg (Energy Institute Vorarlberg) assesses the risk for detached houses: if water is used continuously and thus replaced, legionella is usually not a problem. Pipes that are not used for a longer period of time are particularly critical.

An alternative is a fresh water module. It only heats the drinking water when it is drawn off via a heat exchanger; the cylinder then only contains heating water. This does not require high cylinder temperatures, which, according to klimaaktiv, is particularly beneficial for heat pumps.

What you can check now

• Check the settings: Ask your installer what temperature your cylinder is set to and whether and how often the system heats it up to a higher temperature.
• Flush after absence: If a pipe has not been used for more than three days, the federal state advises running all hot and cold water taps for one to two minutes. After a longer break, flush with hot water for at least five minutes at a low flow rate, placing the shower head flat on the floor and leaving the room briefly.
• Descale shower heads: Limescale and deposits provide a breeding ground for bacteria.
• Circulation: A circulation pump that runs around the clock constantly wastes heat. klimaaktiv advises using a timer, but also warns against switching it off completely for long periods, as the water will then stagnate.

Anyone planning a new heat pump should have the hot water preparation planned at the same time. You can find installers from your region via our request for quotes.