Counter for temperature when 7 days below a specific level

Hy together,

just installed a temperature sensor at my drinkingwatertank. The idea is to safe gas in summer because of the installation of a heating rod. But to be sure the temperature is not to low for some days (f.e. 7) because of legionella, I need a something which gives me a warning.

Warning when the temperature is 7 days below 55°C…

I would appreciate your help.

Thanks a lot in advance.

Nice outlining of the requirements, thanks for this.

Now, could you dig a bit on the technical side of things, please.

  • What sensor?
  • What integration?
  • What do you have?
  • What help are you asking for, exactly?

Before you proceed, I suggest you look up the temperatures required for legionella to stop growing (not die off - important difference):

“Usually, there is no growth above 55°C, and a temperature of over 60°C has a bactericidal effect.”

“These recommendations state hot water must be stored at 60°C inside the water heater by ensuring, at least once a day, the temperature reaches at least 60°C in the entire tank.”


What you’re proposing is to ensure that drinking water only reaches a max of 55°C once a week.
I’m far from being an expert, but the above means that for the rest of the week the temperature can drop way below that and legionella will happily multiply. Then, for the brief period of time you heat up your drinking water, it will (temporarily) stop multiplying.

You’re not killing it - you’re just pissing it off.

I suggest you have a read and revisit your requirements. Once you’re done, come back to us with your new requirements and provide the details @koying mentioned.

In the meantime, don’t drink the water, please.