Cooling Towers and Legionella: The Importance of Water Treatment and Testing to Minimize Risks to Human Health

Cooling towers are utilized in many comfort cooling (HVAC) and industrial process cooling systems.

Legionella, a deadly bacterium, may exist in the warm, moist environments present in cooling towers.

There is a possibility of legionella exposure as cooling tower spray and water mist can enter the air we breathe.

To properly address the risk, it is important to ensure cooling towers are properly maintained and water treatment programs are in place.  

What is Legionella and Legionellosis?

Legionella is a pathogenic gram-negative bacteria that causes legionellosis. Legionellosis varies in severity, from a mild flu-like illness called “Pontiac fever”, to a potentially fatal form of pneumonia known as “Legionnaires’ disease”. 

Legionnaires’ disease can affect anyone. The bacteria are found worldwide in many different natural and artificial aquatic environments including cooling towers and other water systems in:  

Examples of water systems where Legionella may be present include hot tubs, drinking fountains, ice machines, and water displays (fountains). 

Who is At Risk of Legionella?

Although Legionella can affect anyone, certain populations are at a higher risk of getting sick. These include (1, 2): 

  • Individuals aged 40 and older 
  • Present or past smokers 
  • Those with respiratory problems and chronic lung diseases such as chronic obstructive pulmonary disease (COPD) or emphysema 
  • People who are immuno-compromised 
  • Post-transplant or chemotherapy patients 
  • Individuals battling cancer 
  • Those with underlying health conditions, including diabetes, kidney failure, or liver failure 

Understanding the Risks

If not properly managed, cooling towers and other water systems can be a breeding ground for Legionella and create health risks for building occupants and the surrounding population. Building owners are obligated to properly maintain cooling tower systems and in some jurisdictions, develop water management plans under local, provincial, and federal regulations.

Water management plans, water treatment programs, and water testing are tools to evaluate risk and ensure precautions are in place to minimize health risks and local health and safety violations. 

The Importance of Water Treatment in Cooling Towers

Maintaining a clean, properly treated cooling tower is essential to minimize Legionella risk. Water treatment involves methods to control corrosion, scale, and microbial growth to ensure the cleanliness and efficiency of the cooling tower and cooling system. Proper water treatment and maintenance activities are critical to prevent Legionella and Legionnaire’s disease.

How Regular Testing Minimizes Legionella Risk

Regular water testing can identify potential problems. By detecting problem conditions, which may include periodic environmental sampling for Legionella bacteria, the risk to human health can be minimized. Regular water testing ensures your water treatment program is working and allows you to respond to small variances before they become big problems. 

Guardian Chemicals: Ensuring Safe Water Systems

Guardian Chemicals can provide you with clarity on the risks and requirements associated with your cooling systems and Legionella. We design water treatment programs to: 

  • Minimize legionella risk 
  • Protect your people 
  • Protect your equipment  

Guardian Chemicals can assist you in the development and implementation of a water management plan. We also provide onsite testing equipment, services to collect water samples, and access to accredited lab culture testing, PCR or rapid field testing for Legionella bacteria.

Benefits of Partnering with Guardian Chemicals

By working with us, you decrease the risk of Legionella cases and liability associated with Legionella for your tenants, operators, contractors, and the public. Our services can help you score LEED and BOMA Best points, increase tenant and owner satisfaction, and provide peace of mind.

And if you’re curious about how to change water treatment suppliers or need help to find the right water treatment supplier for you, we can help!


The risk posed by Legionella in cooling towers can be effectively managed by implementing a Water Management Plan. The plan surveys the use of water at each point in the building. A proper water management plan covers the entire facility. It includes guidelines on water treatment, periodic environmental testing, system monitoring, maintenance and operating best practices proven to reduce risk.

Learn more about cooling tower maintenance, read the article below:

Start Your Journey to a Safer Cooling Tower Today

When you’re ready, contact us to reduce your Legionella risk and improve the safety and efficiency of your cooling tower system. Together we can create a better environment to protect your employees, customers, and your business reputation. 

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