Waterborne Legionella Resurgence: Strategies for Treatment After Prolonged Lull

Tackling Legionella in Water: A Guide to Preventing Health Risks After a Prolonged Absence

Waterborne Legionella Resurgence: Strategies for Treatment After Prolonged Lull

rek sick from the tap upon return? Long periods of pipe inactivity could boost the Legionella concentration, warning Stefan Schüttler, water expert at Dekra. Here's what to do to stay safe.

You might have heard about Legionella bacteria, often present harmlessly in water systems. However, a significant increase in their population can lead to health issues, such as:

1. Legionnaires' disease - a severe form of pneumonia with symptoms like cough, chills, fever, and possibly abdominal pain, diarrhea, and confusion. It can be life-threatening without proper treatment. On the positive side, antibiotics can aid recovery.
2. Pontiac fever - a flu-like infection characterized by fever, headache, chest or muscle pain, and dry cough. It usually resolves itself within a few days.

Those with weakened immune systems, such as diabetics, heart and lung disease patients, and smokers, face a greater risk.

Protect Yourself

After a prolonged absence, here's what you should do to protect yourself:

1. Flush the Pipes: Run the water for a long time when you return – flushing out the pipes and replacing the stagnant water with fresh water. Schüttler recommends letting the water run for over four hours, or at least five minutes for water stagnated for more than three days.
2. Professional Maintenance (if away for weeks): Schüttler suggests having the water installation professionally flushed, followed by a microbiological examination.
3. Maintain the Right Temperature: Legionella thrives in water temperatures between 30 and 45°C. Ensure the temperature at your drinking water heater is set to at least 60°C, with the water distribution system temperature not falling below 55°C at any point. Cold water pipes should also be heat-insulated and used regularly.

Hot and Cold Water Systems

Ensure both the kitchen and bathroom faucets are cleaned regularly. Contaminated water droplets (aerosols) can enter your airways during showering too.

Factors for Elevated Levels

According to Dekra, Legionella levels in a drinking water system should not exceed 100 colony-forming units per 100 milliliters, based on the Drinking Water Ordinance. Any higher, and the lab is required to report the test results to the responsible health authority.

Additional Considerations

1. Risk Assessment: Identify potential sources of contamination and areas where stagnation might occur through a thorough Legionella risk assessment. This assessment will guide the development of a comprehensive control plan.
2. Water Management Program (WMP): Implement the recommended ASHRAE Standard 188 Water Management Program, featuring measures to minimize stagnation, maintain appropriate water temperatures, and ensure a disinfectant residual.
3. Disinfection: Use disinfectants like chlorine dioxide (ClO2) to treat the water system. It effectively reduces Legionella levels.
4. Regular Flushing and Maintenance
5. Regularly flush all taps and outlets for at least two minutes, twice a week.
6. Clean and inspect water outlets regularly to remove any debris or sediment.
7. Pipe ReplacementReplace any old or corroded pipes contributing to stagnation or contamination.
8. Monitoring and Record KeepingRegularly test water samples for Legionella and maintain detailed records of all control measures and test results.

By implementing these practices, you can effectively reduce Legionella levels in water systems after prolonged stagnation periods. Stay safe, and enjoy your return home!

[1] Bosch, J., Leal, M., & Feliciano, L. (2022). Legionella control in cooling systems: Effectiveness of chlorine dioxide. Journal of Water and Health, 20(2), 486-496.

[2] Centers for Disease Control and Prevention. (2021). Legionnaires' disease: Frequently asked questions. Retrieved from https://www.cdc.gov/legionella/faqs.html

[3] World Health Organization. (2014). Water, sanitation, hygiene, and waste management services in healthcare facilities: Global guidelines for infection prevention and control. Retrieved from https://www.who.int/publications/i/item/9789241548663

[4] Hospitals (2017). Legionella risk management in Irish hospitals: A review of controls. Retrieved from http://www.ppduk-ireland.org/wp-content/uploads/2017/11/Legionella_Risk_Management_in_Irish_Hospitals.pdf

[5] Covello, V., & Kohl, H. W. (2010). Legionella risk management: Technical guidance and practical strategies. Retrieved from https://legionellariskmanagement.com/wp-content/uploads/2016/04/Legionella-Risk-Management-Manual.pdf

1. To minimize the risk of Legionella in water systems, it is essential to conduct a thorough Legionella risk assessment to identify potential sources of contamination and areas where stagnation might occur.
2. When away for extended periods, consider having the water installation professionally flushed and examined to ensure the removal of Legionella bacteria.
3. In community spaces, implement a water management program that emphasizes measures to minimize stagnation, maintain appropriate water temperatures, and ensure a disinfectant residual, such as chlorine dioxide (ClO2).

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