Legionella Control in Water Systems: Steps to Prevent Outbreaks

Legionella is a microscopic bacterium notorious for causing severe lung infections like Legionnaires’ disease and Pontiac fever. Though it occurs naturally in freshwater, problems arise when it multiplies in man-made water systems such as cooling towers, hot tubs, and building plumbing. By recognizing the conditions that favor Legionella growth and taking decisive control measures, you can help safeguard your facility’s water systems and protect occupants.

Where Legionella Thrives

Warm Water Temperatures

Legionella flourishes between 25°C and 45°C (77°F–113°F), making hot water systems, cooling towers, and decorative fountains prime breeding grounds.

Stagnant Water

Unused pipes, tanks, and “dead-ends” create the perfect environment for water stagnation, allowing Legionella to multiply undisturbed.

Biofilms

Microorganisms form a slimy protective barrier on surfaces. This biofilm shields Legionella from disinfectants, making the bacteria harder to eradicate.

How to Control Legionella

1. Temperature Management

   • Keep hot water above 60°C (140°F) and cold water below 20°C (68°F).
   • Monitor temperatures regularly and make necessary adjustments.

2. Flow Optimization

   • Eliminate dead-ends or unused piping.
   • Maintain adequate water circulation to prevent stagnation.

3. Effective Disinfection

   • Use chemical disinfectants (e.g., chlorine) or physical methods (e.g., UV radiation).
   • Ensure proper dosage and application to avoid bacterial resistance.

4. Routine Maintenance

   • Clean and inspect tanks, filters, and cooling towers frequently.
   • Remove or prevent biofilm buildup to inhibit Legionella growth.

Beyond the Basics

1. Risk Assessment

   • Pinpoint vulnerable water systems, such as cooling towers or complex plumbing networks.
   • Identify high-risk populations (e.g., hospitals, nursing homes) where outbreaks can be more severe.

2. Water Management Programs

   • Develop a structured plan that includes regular monitoring, risk evaluations, and control measures.
   • Follow established guidelines like ASHRAE 188 for comprehensive Legionella prevention.

3. Training & Awareness

   • Educate building owners, managers, and maintenance teams about Legionella risks and best practices.
   • Keep records of inspections, treatments, and any corrective actions taken.

Conclusion

Legionella may be a microscopic adversary, but it can cause significant health risks when left unchecked. By implementing temperature control, ensuring water flow, using the right disinfection methods, and maintaining a robust water management program, you can dramatically reduce the likelihood of Legionella taking hold. Consistent monitoring, educated personnel, and proactive interventions form the foundation of effective Legionella control—securing safe water systems for everyone involved.