Prevent Legionella in Cooling Towers
Sunday, September 1, 2019

Prevent Legionella in Cooling Towers

Legionnaires’ disease reports are up fivefold since 2000, as reported by USA Today. What’s worse is that, if left untreated, this disease can be fatal.

Let’s back up. Legionella pneumophila bacteria may be found in untreated or undertreated cooling towers, hot water tanks, pools, spas and large plumbing systems. When this water is sprayed or vaporized through a shower head, faucet, hose or recirculating cooling tower, the droplets can be inhaled, exposing occupants to any legionella that might be present. This exposure may result in Legionnaires’ disease in those who are most susceptible, including people over 50, smokers, and those with chronic lung diseases or cancer, weakened immune systems or other underlying illnesses (

The side effects of Legionnaires’ disease include shortness of breath, cough, fever, body aches, vomiting and even death ( In the U.S. in 2017 alone, more than 7,500 cases of Legionnaires’ disease were reported. Of those who contract the disease, approximately one in every ten will die (USA Today).

Why does this matter? If you operate a cooling tower, naturally occurring trace amounts of legionella may be found in your system. However, in the worst case scenario, high amounts of legionella could expose your tenants, patients, customers, staff or you to this dangerous disease. Scary, right? 

The threat of this health hazard isn’t something over which you should lose sleep. The good news is that the spread of Legionnaires’ disease in your cooling tower is preventable. 

How Do I Limit Legionella Growth?

Legionella grows best in warm water, which is why cooling towers are so appealing for bacteria. To stop and reverse the growth of this bacteria, these systems need to have a cooling tower plan in place that addresses system start-ups, dead legs and mechanical maintenance. Additionally, cooling towers need to be treated regularly with a comprehensive water treatment program. These plans typically include the use of biocide, scale and corrosion control chemicals.

How Do I Monitor Legionella Growth in My Cooling Tower System?

Routine biological testing, via a monthly dip slide test, should be used to monitor the wellness of your cooling tower. The results of these tests should always be documented in a service report as a way to ensure the protection of you and those who regularly inhabit your facility. 

Legionella testing is required each time a cooling tower is started. A legionella test is recommended if rooting biologic testing exceeds cooling plan limits. Should a routine test return positive results for legionella, disinfection of the cooling tower is mandatory, followed by an additional test for the bacteria. The disinfection and test cycle will continue until the legionella is no longer present.

Why Should I Trust State® to Treat My Cooling System?

State’s comprehensive service-oriented cooling system treatment plan aligns with the stringent and strictest water treatment industry standards. State’s cooling system plan includes the treatment, testing, maintenance and documentation of cooling tower systems, assuring you that your system meets the highest standards of operation. You can thank us later for the extra sleep.

Want to Know More About State’s Cooling System Plan?

Let us reduce your worry over the health and safety of your employees, clients, staff and visitors. To be put in contact with your local account manager, please call (877) 747-6986.


Alltucker, K. (2019, February 19). Legionnaires' disease reports up more than fivefold since 2000; oversight is lacking. Retrieved March 05, 2019, from

Legionnaires Disease | About | CDC. (2018, February 13). Retrieved March 7, 2019, from