Testing for Legionella Bacteria: The Smart Way to Validate a Water Management Program

Part 1 of a 3-Part Series of interpreting the CDC’s latest Legionella bacteria sampling guidance

By Hilary Nardone, Environmental Group Training Manager
Certified ASSE 12080 Legionella Water Safety and Management Specialist

Implementing a Water Management Program (WMP) at your facility is an important step in controlling Legionella bacteria growth and transmission.  A robust WMP must be validated for effectiveness in its objective of controlling Legionella bacteria. Per the Centers for Disease Control and Prevention’s (CDC), routine environmental sampling for Legionella bacteria is a helpful strategy [1].

Why is testing for Legionella bacteria the smart way to validate a WMP?

Validation is required in ASHRAE Standard 188-2021:

Section 6.2.8 of ASHRAE Standard 188-2021 states that “the Program Team shall establish procedures to confirm, both initially and on an ongoing basis, that the Program, when implemented as designed, controls the hazardous conditions throughout the building water systems.”  Testing for Legionella bacteria is an objective way to confirm if the monitoring of control locations identified in the WMP are working effectively.

Image via CDC

Validates WMP control measures are effective:

Sampling for Legionella bacteria allows for the WMP Team to ensure that the control measures that were implemented in the WMP are effective at controlling bacteria growth and amplification.  Non-detect Legionella bacteria samples signal that the control location’s limits, monitoring, and corrective actions are working at your facility.  On the other hand, having positive Legionella bacteria samples after implementing your WMP signals that your document may need some adjusting.  Often this involves reviewing and modifying the monitoring, control limits, and corrective actions for the identified control locations.  For example, a hot water tank tests positive for Legionella bacteria.  Upon review, the WMP Team determines that the facility’s tanks are heated to 125°F and are never cleaned.  As an adjustment to better control Legionella bacteria, the WMP Team decides to increase the temperature to 140°F, circulate the tanks, and clean and disinfect the tanks annually.  Non-detect follow-up Legionella bacteria samples confirm this to be an appropriate step in controlling bacteria growth and amplification.

Barclay Water Management, Inc. has created, implemented, and validated hundreds of complete Water Management Plans (WMPs). In partnership with our customers, Barclay Water Management is dedicated to ensuring its WMPs comply with national and local standards and guidelines including ASHRAE Standard 188, the Joint Commission, Department of Veteran Affairs, and local Health Departments.


[1] CDC recent publication, “Toolkit for Controlling Legionella in Common Sources of Exposure” (Legionella Control Toolkit)

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