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Legionella Sampling Locations

Sampling is the single most important activity for every project. The purpose of sampling is to identify the goals of the project, to answer specific questions, or to develop a hypothesis to test. While it is normal for clients to be upset when they encounter a suspected case or an outbreak, avoid taking random samples without understanding how the data will be used and who could ultimately see the results first.

Here are some key questions to consider that will help you focus your sampling efforts:

  1. What are the appropriate test methods and the level of detail needed for your project? (See test codes)
  2. Where do you need to sample? Are there particular types of equipment or devices that need to be sampled?
  3. When do you need to sample? Consider there may be times to take cooling tower samples in the summer and early fall to account for worst case scenarios rather than taking strictly periodic samples.
  4. How many samples do you need to take?

It is important to take as many samples as necessary to obtain sufficient data to answer your questions. Every sampling location should provide data to answer a question however, avoid taking more samples than necessary. Understand that one sampling point or one sampling event will not constitute a representative number of samples and will not pass a legal challenge. The purpose of sampling will vary according to different project goals so adjust your sampling strategies accordingly. Use the “Where to Look” and “Sample Locations” sections to help focus your activities.

If you represent a Veterans Administration Medical Center, understand the required test codes and sampling locations before doing any sampling. Review the VHA Directive dated August 2014 which can be found at this link: http://www.va.gov/vhapublications/ViewPublication.asp?pub_ID=3033

Cooling Tower Sampling Locations - Sample Quarterly

  • Tower Makeup
  • Tower Sump away from makeup * (water and swab)
  • Inlet to Heat Exchanger
  • Outlet from Heat Exchanger
  • Distribution Pack
  • Tower Pack * (water and swab)

Potable Water Sampling Locations - Sample Semi-Annually

  • City Water Main Entry Point
  • Storage Tanks
  • Hot Water Heater Drain Point *
  • Hot Water Return
  • Last Point on Cold Water/First Point on Hot Water
  • Last Point on Hot Water*/First Point on Cold Water
  • 10% of Selected Outlets (water and swab)
  • Ice Machines
  • Drinking Water Fountains

* Test Routinely
Test all locations to establish a baseline
Test all locations during an outbreak or when suspected case is identified

If you have any questions, call Diane Miskowski at 1-800-220-3675 x2528

For technical questions please call:


Christopher Goulah, PhD

Legionella Technical Manager

EMSL Analytical, Inc.

Depew, NY 14043

716-651-0030 ext. 1407


Latest Article

An Overview of Legionella Analyses

By Diane Miskowski, MPH EMSL Analytical, Inc.

The first recognized outbreak of Legionnnaires' Disease occurred in the US at the American Legion Convention in Philadelphia during the summer of 1976. read more...

Additional Resources

For additional information please click the links below.

Legionnaires' Disease
Clinical Microbiology Reviews
Cooling Technology Institute
more resources...

Legionella images courtesy of CDC, Public Health Image Library (PHIL)

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