ᐅ Lowering the Hot Water Temperature in a Single-Family Home

Hello,
in many discussions here, I have read that lowering the hot water temperature can save energy because there is generally no risk of Legionella bacteria in single-family homes.
Now the question is, is this also scientifically proven? My wife is really concerned about this and would like to have well-founded expert knowledge.
We have a 300L (79 gallons) hot water tank, three taps that are all used daily, and we also shower every day. In my opinion, lowering the hot water temperature is an economic mistake, and I want to adjust the temperature so that during the hottest showers the water heated in the tank can be used directly without mixing in cold water.
Is this really safe? Our old gas boiler does not have a Legionella prevention program.
Thank you for your evidence-based responses.

I think the same way as you do... warming up first and then mixing also sounds illogical to me. However, I can’t add anything scientific to that.. 😉

My landlord in this five-unit rental building raises the hot water storage temperature to 60°C (140°F) for one day every two weeks and then lowers it again. The heating system is already about 12 to 13 years old. I assume this could be programmed, but he is not dealing with that at the moment. Instead, he has put the biweekly temperature increase on his calendar.

So, if your heating system doesn’t have a built-in legionella control program yet, you have to do it manually. However, this should be easily manageable.

Legionella bacteria develop (almost) exclusively in stagnant water.
If you regularly take showers in a single-family home, the hot water in the tank is circulated and renewed quite often. Therefore, there is no risk here.
Additionally, Legionella bacteria are inhaled through the respiratory tract. The risk exists ONLY when showering (spray mist) and not from drinking the water.
Hot water can therefore be safely reduced to 45°C (113°F).

Edit: Normally, shower water temperature ranges between 30-38°C (86-100°F).

The maintenance company for my heat pump lowered the temperature from 50°C (122°F) to 45°C (113°F) in April to save energy, with a volume of 300 liters (79 gallons).

Alessandro schrieb:

So, the domestic hot water can be safely lowered to 45°C (113°F).

Thank you for your reply. Reliable sources would be helpful here to convince the rest of the family as well.