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Legionella.io

Free tool · Checker

Temperature danger-zone checker

Type a stored or outlet temperature to see where it sits against the commonly cited control figures. Updates as you type.

°C
The commonly cited figures
  • Below ~20°C: Legionella is largely dormant — keep cold water below this.
  • ~20–45°C: the growth range — the zone to avoid in stored or stagnant water.
  • ~50°C+ at outlets, ~60°C stored: the hot-water control regime.

Guidance figures, not a verdict on your system; your risk assessment sets the targets. Source: HSE — hot and cold water. Mind scald risk where vulnerable people are exposed.