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Summer Cooling Tower Advisory: Disinfection Recommendations

Hot temperatures may impact cooling tower operation. How to better monitor water quality during hotter summer months?

With heat waves and the rise in extreme temperatures across the United States, it is important to remember that high summer temperatures may impact cooling tower operation. Some states, such as New York, have recently issued cooling tower advisories and required summer hyperhalogenation to prevent ideal conditions for the growth of Legionella bacteria.

It is important to closely monitor water quality during hotter summer months when Legionella and other bacteria can multiply quickly. This may require temporarily performing seasonal hyperhalogenation of the cooling tower system, raising free residual oxidant targets, adjusting cycles of concentration or performing supplemental biocide additions. 

By dosing cooling tower systems with higher-than-normal levels of chlorine- or bromine-based biocide, for example, building owners and maintenance staff can add an extra layer of protection to help prevent ideal conditions for Legionella growth.

In addition to preventative maintenance for cooling tower systems, Legionella should be considered to ascertain the need to perform enhanced disinfection procedures and validate the efficacy and effectiveness of maintenance procedures or corrective actions. 

Many of the new and proposed changes to these regulations come in response to advice from the Centers for Disease Control and Prevention (CDC) to “consider changing building and public health codes to include Legionella water management programs.”

Please see the HPE resources below for additional information on Legionella Risk Management Plans, Legionella sampling and collection, CDC Legionella sampling procedures and understanding Legionella test results. 

If you have further questions or require guidance on Legionella sampling and procedures, please reach out to HPE’s Microbiology experts for assistance. HPE Director of Microbiology Jonathon Hall can be reached at or by calling our offices during business hours at 703-471-4200. 

“Operate at the lowest possible water temperature outside Legionella’s favorable growth range (77–113°F).”

-Centers for Disease Control and Prevention (CDC), Legionella Control Measures for Cooling Towers

Does HP Environmental have any free resources about Legionella?

Yes, HPE is happy to provide resources on Legionella and Legionella sampling free of charge. If you should have any additional questions about Legionella, building maintenance, collecting samples or environmental concerns, please do not hesitate to contact our offices at 703-471-4200 or email us at

Legionella Sample Collection Procedures

Understanding Legionella Test Results

Legionella Sample Procedures (CDC)

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