How to Reduce Legionella Risk in Construction Projects

Work involving water or poorly maintained water systems might expose construction workers to Legionella, a bacterium that poses serious health risks. Legionella bacteria thrive in stagnant water, making construction sites with water systems vulnerable to contamination.

This blog discusses what legionella is, its risks and effective strategies to reduce these risks in construction projects. It also explores training programmes to help prevent legionella exposure on construction sites.

What is Legionella?

Legionella is an infectious bacteria found naturally in freshwater environments like lakes, streams and water systems where the temperature is high enough to encourage growth, e.g. hot tubs, hot water systems, water storage tanks, large plumbing systems and decorative fountains.

When these systems are not adequately maintained, legionella can proliferate, increasing the risk of illnesses collectively known as Legionellosis. This includes Legionnaires’ disease, a serious and potentially fatal form of pneumonia, and Pontiac fever, a milder illness resembling the flu.

Risks Associated with Legionella Exposure

Exposure to legionella can lead to significant health risks, primarily by inhaling aerosolised water droplets containing the bacteria. In a construction setting, this can occur through activities involving water systems, such as plumbing, heating and cooling, especially in renovation or repair projects. The risks are heightened for older individuals who smoke, have chronic lung disease or have weakened immune systems. In severe cases, Legionnaires’ disease can lead to respiratory failure, septic shock or acute kidney failure.

How to Reduce Risks Associated with Legionella Exposure

Reducing the risk of legionella in construction projects involves a multifaceted approach:

●    Water System Management Plan

Implement a comprehensive water management programme that identifies potential sources of Legionella growth and ways to minimise them. This includes regular maintenance and cleaning of water systems, proper chlorination and temperature control.

●    Regular Testing

Conduct periodic water tests to detect the presence of legionella, especially before starting new projects or reactivating systems after a period of disuse.

●    Control Water Temperatures

Maintain hot water temperatures at or above 60°C (140°F) and cold water temperatures below 20°C (68°F), as Legionella bacteria thrive in temperatures between 20°C (68°F) and 45°C (113°F).

●    Avoid Water Stagnation

Ensure water does not stagnate anywhere in the system. Flush out systems before use, remove unused pipes and ensure regular flow in all areas of the water system.

●    Use of Biocides

When necessary, use biocides to control legionella growth, following safety regulations and manufacturer instructions.

Recommended Training to Reduce Legionella Risk in Construction Projects

Training is vital in equipping construction personnel with the knowledge and skills to effectively reduce Legionella risk. Some important training programmes include:

●     Legionella Awareness Training

Legionella awareness training programme educates workers on the health risks posed by legionella and the environments where they thrive. It teaches them how legionella spreads and how to control its risks.

●     Water Hygiene Training

Water hygiene training emphasises Legionella risk awareness and prevention, highlighting the significance of clean water systems in preventing Legionnaires’ disease. It equips workers with knowledge of monitoring, disinfecting and upholding water quality standards.

Legionella Risk Assessment Training

Legionella risk assessment course equips workers with the knowledge and skills to identify and evaluate the risks associated with legionella in water systems. It helps them conduct comprehensive assessments and implement appropriate control measures to minimise the risk of Legionella proliferation and exposure.

●     Legionella Management Training for Water Systems

Legionella management training for water systems provides workers guidance on maintaining water systems to inhibit legionella proliferation. The training programme highlights the importance of regular inspection, cleaning and disinfection of water systems to ensure these systems remain free from bacterial contamination.


Legionella risk in construction projects is significant but manageable with the proper knowledge and practices. Construction projects can significantly reduce the likelihood of an outbreak by understanding legionella, recognising the risks and implementing effective prevention and control measures. Training and awareness programmes also empower construction teams to maintain safe working environments.

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