Water Sampling for Legionella & Total Coliform

Water Sampling for Legionella & Total Coliform

This technical bulletin provides guidance on water sampling procedures for Legionella and Total Coliform bacteria. Legionella poses a significant health risk, particularly in large buildings with complex water systems, while Coliform bacteria contamination can be a sign that a possible health risk exists for individuals exposed to contaminated water.

Background

Legionella bacteria thrive in warm water environments such as cooling towers, hot water tanks, and plumbing systems. Inhalation of contaminated water droplets can lead to Legionnaires’ disease, a severe form of pneumonia. Routine sampling is essential for identifying contamination risks and ensuring compliance with regulatory standards. Coliforms bacteria are a collection of microorganisms that live in large numbers in soils, plants, and the intestines of warm-blooded (humans) and cold-blooded animals.

Regulatory Compliance

• ASHRAE Standard 188: Establishes guidelines for Legionella risk management.
• CDC Toolkit: Recommends best practices for Legionella control.
• GSA Guidelines: Require routine water testing in federally managed buildings.
• Ohio Administrative Code Rule 3701-22-07 and Rule 3701-16-12: Require implementation of an effective water management program.
  • Specific to Hospitals and Residential Care Facilities
• Ohio Administrative Code Rule 901:3-62-05: Require sampling of water at water bottling plants for sanitary facilities.

Sampling Locations for Legionella

Water samples should be collected from the following locations for legionella:

• Cooling towers
• Domestic hot and cold-water outlets
• Decorative fountains
• Hot water storage tanks
• Ice machines
• Areas where water stagnation may occur
• Include cold water samples from the incoming water mains, and representative samples from both proximal and distal locations on each hot water loop.

Sampling Procedures Legionella

• Sampling Procedure and Potential Sample Sites: Protocol for collecting environmental samples for Legionella culture during a cluster or outbreak investigation or when cases of disease may be associated with a facility.

Sampling Procedures Coliforms

• Collect total coliform and coli samples according to The Colitag^® System, which is an EPA-approved method.

Risk Mitigation Strategies

• Maintain hot water systems at 120–140°F to prevent Legionella growth.
• Flush infrequently used outlets regularly.
• Conduct periodic disinfection of plumbing systems.
• Implement a water management plan per CDC and ASHRAE guidelines.
• Reduction of coliform contamination includes water filters and other water-treatment devices which should be changed and maintained in accordance to the manufacturer’s recommendations.

Conclusion

Routine Legionella and total coliform water sampling is crucial for maintaining safe water systems in facilities. Adherence to best practices ensures compliance, reduces health risks, and supports proactive water quality management.

References

• American Society of Heating, Refrigerating, and Air-Conditioning Engineers. (2018). ASHRAE Standard 188: Legionellosis: Risk Management for Building Water Systems.
• Centers for Disease Control and Prevention. (2021). Toolkit for Controlling Legionella in Common Sources of Exposure. Retrieved from https://www.cdc.gov/legionella/wmp/toolkit/index.html
• General Services Administration. (2020). Water Quality Management Guidelines.
• International Organization for Standardization. (2017). ISO 11731: Water Quality—Enumeration of Legionella.