Due to the current energy crisis, the authorities have various proposals for, and requirements for, saving on energy. Among other things, you can lower the temperature in hot water systems, and you can use less hot water by e.g. taking shorter baths, washing your hands in cold water and installing water-limiting measures, e.g. energy-saving showers.
However, both parts can contribute to increased growth of Legionella pneumophila in the water systems with a risk of infection and disease. It is therefore important that Danes think carefully before saving on energy.
Hot water systems can cause severe pneumonia
Most of our hot water systems contain Legionella pneumophila . The bacterium can cause a serious pneumonia called Legionnaires’ disease. Infection occurs by inhaling atomized water that is contaminated with the bacteria, e.g. while showering.
“The disease particularly affects elderly and debilitated people and causes up to 300 hospitalizations per year, but the bacterium is presumably the cause of far more mild cases of the disease, also in younger people. Since the bacteria are common in our hot water systems, it is important to limit their growth. This happens at home primarily by ensuring that cold water is no more than 20 °C and that hot water is at least 50 °C, as the bacteria cannot grow at these temperatures and begin to die at 50 °C,” says Søren Anker Uldum , who is head of department at the Statens Serum Institut.
Rinse through with very hot water
It is therefore important to continue to maintain at least 50 °C throughout the hot water system. The temperature must be reached at all tapping points after no more than 30 seconds. rinse and in the return water (before hot water tank or heat exchanger). In most cases, this can be achieved by heating the hot water to 55 °C in the hot water tank.
With reduced consumption of hot water, the water has longer residence times in the pipes and can have temperatures in the bacteria’s growth area for a longer period of time, so there must be a certain consumption of hot water.
Taps, such as faucets and showers that are rarely used, should be flushed with hot water at a minimum of 50 °C for a few minutes at least once a week.
When showering (which may well be short), it is also a good idea that at least once a week you first set the mixer to the maximum temperature and let the water run (to the drain) until it is as hot as it can be before setting it to bath water temperature (approx. 36 °C).
This advice applies especially if there are vulnerable people in the household or institution, such as the elderly or people with chronic illness or a weakened immune system.
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