Definition
Legionella protection is the set of design and operating measures that stop Legionella bacteria multiplying in stored or circulating hot water, where they thrive between 25 °C and 45 °C. The main measures are keeping stored drinking water at 60 °C and circulation returns at 55 °C or above, running a periodic anti-Legionella heat-up cycle (many heat pumps do this weekly), or avoiding storage altogether with hygienic tanks and fresh-water stations. The EU Drinking Water Directive 2020/2184 requires risk-based Legionella monitoring in buildings.