How does temperature affect legionella?

Temperatures What happens to the Legionellae at this temperature
below 20°C The organism can become dormant at much lower temperatures and return to active multiplication whenever more favourable conditions occur.
between 20°C and 37°C Multiplication increases as the temperature rises above 20°C and reaches the peak at 37°C.
between 37°C and 46°C Multiplication slows down after 37°C and ceases around 46°C.
approx. 50°C The environment becomes slightly hostile to the bacteria, some of which will be killed in a few hours.
approx. 60°C The environment becomes very hostile to the bacteria, most of which will be killed in a few minutes.
approx. 70°C The bacteria are killed virtually instantaneously.

L8 states you must maintain your temperatures as follows:-

Cold Water Outlets

These must be below 20°C within 2 minutes of running the outlet.     Frequency of Testing Details

Hot Water Outlets (excluding showers and any outlet controlled by TMV)

These must be above 50°C within 1 minute of running the outlet.


The water must be stored at 60°C and any return back to the calorifier should be at least 50°C

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