ᐅ Hot water set to 60°C due to risk of Legionella bacteria

Created on: 29 Jul 2021 08:28
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Pädda
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Pädda
29 Jul 2021 08:28
Hello.
It is often recommended to set the hot water temperature to 60°C (140°F) on the heating system when using a boiler (in our case, a 300L (79 gallons) unit with gas heating) as a precaution against Legionella bacteria. Since my family’s health is the top priority, I don’t mind that. What I don’t understand is whether the hot water should be maintained at 60°C (140°F) continuously for 24 hours, or if it is recommended to turn off the hot water preparation at night using a timer. If you switch it off at night, it seems somewhat inconsistent because the water would cool down again and drop below the recommended 60°C (140°F).
Do you have any opinions on this?
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halmi
29 Jul 2021 09:05
With gas, you can set the temperature to 60°C (140°F), which isn’t particularly harmful. However, proper circulation is actually quite important in that case.

In my opinion, for typical household use by a standard family of four, 300 liters (approximately 80 gallons) is sufficient to avoid hygiene issues even at lower temperatures.
kati133729 Jul 2021 11:40
I already started a thread about this before and did a lot of research online. We also have a legionella prevention program, using an air-to-water heat pump.

The information on the web is contradictory. In this forum, the general consensus was that this probably doesn’t cause any problems.

My solution is simply to empty the storage tank completely from time to time. Bath the child in the evening, then relax by taking a shower yourself – eventually cooler water comes through. I believe that if you manage to do this regularly, you will have fewer issues with legionella.

By the way, legionella bacteria are only a health risk if inhaled as an aerosol (for example, when showering), not when drinking water.
Tolentino29 Jul 2021 11:51
mh tasty legionella shake.

If you are very cautious, you can also heat the storage tank up to 70°C (158°F) once a week. The best time for this is around midday using photovoltaic energy.
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Pädda
30 Jul 2021 07:21
Pädda schrieb:

What I don’t understand is whether you should set the hot water to 60 degrees Celsius (140°F) continuously or if it’s recommended to turn off the hot water system completely at night using a timer. If you turn it off at night, it wouldn’t be consistent, because the water cools down and falls below the recommended 60 degrees Celsius (140°F).

Do you have any opinions on this? It’s common practice to switch off hot water preparation during the night.
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hampshire
30 Jul 2021 07:41
The risk of legionella is very low with the small volumes that are used frequently. You can find good information from the DVGW, which provides well-prepared documents from a reliable source.

I keep our hot water storage tank with integrated heat pump permanently set to 58°C (136°F). There is no circulation pump. The pipes are short and used daily. Once I have connected the photovoltaic system (at the moment I’m too lazy to lay the cable), the tank will receive some power from it. In summer, this should be enough to keep the heat pump switched off.

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