Legionella cycle
A planned run that heats the stored hot water hotter than usual, to help control legionella bacteria.
HSE guidance gives 60 °C or above for stored hot water where temperature is the control. The system's design and instructions set when the cycle runs and how hot it gets, sometimes with a backup heater.
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Sources
Sources checked 31 October 2026. Guidance, grants and official pages can change.
- HSE: Legionnaires' disease, things to considerHSE's guidance on hot water stored at 60 °C or above, reaching 50 °C within a minute at outlets, and cold water kept below 20 °C.