safe drinking water standards | legionella detection

What You Need to Know About Legionella

Ensuring your water system is clean and hygienic is extremely important – failing to do so can result in harmful bacteria that cause infections and diseases in humans. Legionella are one such bacteria; they can cause infections like Legionnaires’ disease, Pontiac fever and Lochgoilhead fever. These are all encompassed by the blanket term ‘legionellosis’, which refers to any infection caused by Legionella bacteria.

H2O Comply can help you control the risks presented by Legionella and other water-borne bacteria, but it will always be beneficial for you to know the basics. Keep your water, yourself, and anyone who has access to your water supply safe with this quick guide to Legionella bacteria.]

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What are Legionella bacteria?

Legionella are rod-shaped bacteria that cause legionellosis infections in humans. While around 60 species of Legionella have been identified, the Legionella Pneumophilia species is reported to be responsible for approximately 90% of human infection cases.

Legionella is naturally occurring and can be found in watercourses, soils, composts, and other aquatic or moist environments. They can also find their way into buildings’ water systems.

Water Sampling | Water Testing | Water Analysis for legionella testing

What are the medical implications of Legionella?

While the Pontiac and Lochgoilhead fevers are non-fatal, flu-like illnesses, Legionnaires’ disease is a form of pneumonia that can be fatal, especially if left untreated. Symptoms include a cough, difficulty breathing, chest pain, a high temperature, and flu-like symptoms.

Legionellosis infections can only be contracted by the deep inhalation of tiny water droplets – known as aerosols – that are contaminated with Legionella bacteria. These droplets can be produced by air conditioning systems, hot tubs, rarely used taps and showers, decorative fountains, and humidifiers.

These infections usually cannot be contracted by drinking water that contains the bacteria, coming into contact with other people with the infection, or exposure in freshwaters such as ponds or rivers.

Where do Legionella grow?


Legionella occur naturally and can be found in a range of natural and artificial water systems, such as lakes, rivers, and soils. This also means they can be found in mains water supplies, albeit in low numbers, so it’s likely they’ll find their way into buildings’ water systems.

Generally, the low amounts of Legionella in freshwater do not lead to disease. However, they can pose a health risk when they make their way into buildings’ water systems and multiply. Legionella bacteria require iron to grow, so multiply rapidly in nutritious environments created by things like rust, sludge, scale, algae, and other bacteria. They also thrive in stagnant water.

Legionella have been found in water systems ranging in temperature from 6°C to 60°C, although they grow best between 20°C and 45°C. These harmful bacteria can be killed rapidly at temperatures above 60°C, and they do not multiply at temperatures above 50°C or below 20°C. However, they can remain alive until the temperature rises to a suitable level for multiplication unless they are dealt with.

How can H2O Comply Help?

If you’re worried about your water system, H2O Comply can help. We are a team of specialist water treatment engineers you can trust, providing everything from legionella risk assessments and monitoring to microbiological sampling. Our experts are committed to keeping yourself and your water system safe, and making sure your property is compliant with all relevant regulations in the process.

 Contact us today to find out more about our services.

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Want to find out more about water borne bacteria and how proper testing can help prevent its spread? Legionella, a potentially harmful bacterium, poses health risks when present in water systems. Understanding Legionella and implementing rigorous testing measures is crucial to mitigate its spread and protect public health. Read our other articles about the various testing methods available, their importance in early detection, and how they contribute to effective prevention strategies. Explore how proper testing not only identifies potential sources of Legionella but also aids in the development of targeted control measures, ensuring safer water systems for all.

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