Legionella are bacteria that cause Legionnaire’s disease, which can be fatal under certain circumstances. They can be found in almost all natural waters and wetlands.

They occur in lakes, ponds, rivers, sewage, thermal baths and drinking water pipes. Legionella are also commonly found in cooling systems with cooling towers. Conditions for their reproduction are ideal in man-made water systems.

The concentration of legionella in water depends above all on temperature, pH value, the presence of other microorganisms (bacteria, protozoa, algae) or substances (organic material, iron salts, calcium, magnesium, rubber, silicone and plastic) and other unknown factors.