Legionella bacteria live naturally in a wide variety of natural and artificial water systems, such as lakes, rivers and soils and so and are very likely to enter a building’s water system, no matter what precautions are in place.

However, they will enter a building’s water systems in very low numbers, it is when they start to grow and multiply do they become a health risk.

If the legionella gets the chance to grow it needs a way to spread and any source that generates aerosol or a fine mist of water has the potential to transmit Legionella. This is why you must manage your water systems effectively; to minimise the risks and prevent growth. 

The three key elements contribute to Legionella risk:

• Intrusion introduces Legionella into the system
• Growth occurs when Legionella increases within the system
• Transmission happens when aerosols, or small water droplets, containing Legionella are inhaled

Getting into your system

Peer-reviewed studies indicate that drinking water systems are the primary source of Legionella bacteria and Legionnaires’ disease. The bacteria can become a health concern when they grow and spread in human-made building water systems like;

• Showerheads and sink faucets
• Cooling towers (structures that contain water and a fan as part of centralized air cooling systems for buildings or industrial processes)
• Hot tubs
• Decorative fountains and water features
• Hot water tanks and heaters
• Large, complex plumbing systems

Legionella contamination can occur when water supply systems are improperly maintained, leading to an environment that feeds Legionella growth.

Growing in your system

The key to preventing Legionnellais to prevent Legionella growth. Legionella can colonize in water delivery lines and building plumbing systems, contaminating water supplies after the water has been centrally treated at a public water facility.

Parts of a water system with insufficient circulation or lukewarm temperature can provide the ideal environment for Legionella growth.

Legionella bacteria will grow best between 20°C and 45°C, it will rapidly be killed at temperatures above 60°C, and do not multiply at temperatures above 50°C. They will not multiply at temperatures below 20°C either but can remain alive until the temperature rises to a level allowing multiplication to occur. In addition to appropriate temperatures, Legionella bacteria require nutrients to enable them to multiply. These nutrients are found in the water systems and include other common water organisms, sludge, scale and sediment. Legionella bacteria also require iron to grow, which is often provided by corrosion.

Control Methods

To help control the growth of Legionella bacteria the following can be implemented;

• Cold Water: If you can manage the cold water temperatures throughout the system to ensure that cold water is stored  below 20°C and distributed to all outlets within two minutes of opening the tap below 20°C then the cold water circuit will not encourage bacterial growth including legionella growth.
• Hot Water: Hot water should be stored at 60°C and distributed and supplied to all outlets above 50°C within 1 minute of operation.
• Stagnation: Stagnation can be prevented by introducing routine flushing programmes and reducing the volumes of stored water.
• Chemical Control: We always use chemicals as the last line of defence, and we always explore the fundamental measures for control and management before embarking upon or recommending any chemical treatment programme for domestic systems.

Conclusion

Everyone wants safe, clean water when they turn on the tap. However, keeping potable and non-potable water supply systems safe can be challenging, as underground water infrastructure ages or becomes outdated and as newer types of water supply systems and lower flow rates keep water in pipes longer.

Legionella bacteria is a specific form of bacteria which can be very dangerous if an outbreak occurs, unfortunately not much can be done to stop this entering your water system, BUT a lot can be done to prevent the growth and transmission of it.

You should speak to water treatment specialists to ensure the water you are supplying is safe. At Aquachem we have an inhouse microbiologist who provide precise recommendations and advice, contact us to find out more.