Legionella Bacteria & The Role of Temperature

Legionella bacteria naturally exist in places like ponds, rivers, and lakes. However, it can also grow in artificial water systems, such as fountains, waterparks and boilers. When it enters a building’s water system, it can pose serious health risks and lead to Legionnaires’ disease if people inhale droplets of contaminated water. Poorly maintained water systems create an environment where Legionella can thrive, turning it into a potential hazard.

At Acorn, we have years of experience in testing for Legionella bacteria. If you think your water is contaminated, get in touch with our friendly team for expert advice.

Understanding how temperature affects the growth of Legionella is one of the most important parts of keeping your water systems safe. To help you get to grips with this bacteria, we will cover the following topics:

• Legionella and water systems
• What temperature kills Legionella?
• The impact of temperature on Legionella growth
• Managing water temperature to prevent Legionella
• Legionella testing and monitoring

Legionella and Water Systems

Legionella bacteria can quickly multiply in various water systems, posing a threat to human health. Cooling towers, with their warm temperatures, provide an ideal environment for Legionella growth. Hot water tanks, spas, and decorative fountains can also become breeding grounds if not properly maintained and disinfected.

Once Legionella enters these water systems, it forms biofilms (a layer of slime) on interior surfaces, releasing contaminated aerosols into the air. It’s when people inhale these aerosols or droplets that they can catch Legionnaires’ disease, which has common symptoms of a high fever, cough, muscle aches, and shortness of breath.

The impact of temperature on Legionella growth

Temperature plays a big role in the spread of Legionella bacteria, making it an important factor in water system management. Legionella thrives in temperatures between 20°C to 45°C (68°F to 113°F), which is known as the “temperature danger zone”. Within this range, the bacteria can rapidly multiply and pose a significant health risk to people exposed to contaminated water droplets.

Below 20°C, Legionella becomes dormant and unlikely to cause harm, they also stop multiplying in low temperatures. Since it can’t survive in high temperatures, the bacteria will begin to die off in temperatures above 50°C.

Maintaining water at 50°C for two hours kills 90% of bacteria. Raising the temperature to 60°C achieves the same result in just two minutes. Hitting 70°C instantly eliminates all Legionella bacteria present.