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Legionella - A Brief Overview

Legionella (the cause of legionnaires disease) is a type of bacteria found in fresh water environments. Once legionella finds its way into an enclosed environment, such as a building's cooling tower system, it can quickly multiply and spread throughout the building's water system. Contaminated water droplets that are dispersed into the air and inhaled can lead to the development of legionnaires disease.

 About Legionella Bacteria & Legionnaires Disease

​Legionnaires (lee-juh-nares) disease is a serious type of pneumonia (lung infection) caused by legionella bacteria. Signs and symptoms of legionnaires disease can include shortness of breath, cough, headaches, muscle aches and fever (also referred to as pontiac fever). The good news is that legionnaires disease can be treated with antibiotics. Depending on the severity of the symptoms, hospitalization may be required to treat the disease and bacteria.

Self diagnosing can be difficult, as the symptoms can easily be mistaken for an acute fever. Certain individuals are more at risk than others to catching legionnaires disease, these individuals include those:

  • Who are and were smokers
  • Having chronic lung disease
  • Having a weakened immune system
  • Who take medication that adversely effects the immune system
  • That are over the age of 50


 Growth & Spread Of Legionella

​Legionella can grow in any section of the building's water system, such as; storage tanks, cooling towers, water heaters, water filtration systems, aerators, faucets, showerheads, ice machines, hot tubs and more... These devices can easily spread contaminated water droplets throughout your facility. Showerheads, water fountains and cooling towers are great examples of how the bacteria can be aeresolized by a water system. A contaminated cooling tower can easily spread the legionella bacteria to nearby cooling towers; the amount of mist generated by cooling towers along with heavy winds can easily enable the bacteria to travel.

A large outbreak in 2015 affected more than 120 people in the South Bronx of New York, 12 of whom died. Health officials ordered the disinfection of cooling towers, as a nearby hotel's cooling tower was implicated in the outbreak. The water systems listed above can become incubators, feeding the growth and spread of the bacteria. Below are four common building factors that can lead to the growth and spread of legionella;

  • Biofilm, Scale & Sediments: Protects the legionella bacteria from disinfectants and provides food for growth.
  • Water Temperature: The bacteria grows best in warm conditions (77F - 108F), but can still grow outside of these temperature ranges.
  • Changes In Water Pressure: Can dislodge biofilm and sediment, contaminating surfaces downstream. Water stagnation also enables biofilm growth, creating more protection for the bacteria.
  • Inadequate Disinfection: Your current chemical program does not kill or inactivate the legionella bacteria.

The potential for an outbreak makes it important that we take precautions in ensuring our water treatment systems are bacteria free.

 Prevention Measures

​Unfortunately there are no vaccines that can help prevent legionnaires disease. The key preventative measure is making sure that the building's water system is well maintained and routinely tested for legionella and other bacteria.

 Legionella Standard

​ANSI/ASHRAE Standard 188-2015 Legionellosis: Risk Management for Building Water Systems


On June 26th, 2015 an ASHRAE standard was created providing details and guidance on preventing and minimizing the risk of legionella bacteria growth in water systems. The American National Standards Institute (ANSI) approved ASHRAE Standard 188-2015, and is being enforced by agencies that are directly involved with  assuring the safety of building occupants.

Unfortunately the standard does not provide a large amount of guidance when it comes strategies and testing limits on how to minimize the risk of legionella bacteria. The standard instead focuses on the creation and implementation of a documented risk management process.

Who Does The ASHRAE Standard Apply To?

The standard applies to any human-occupied building. It is intended for those who maintain, operate, design, build and/or manage building water systems (recreational, potable and non-potable). These buildings include but are not limited to the following:

  • Multiple housing units with one ore more centralized heating units
  • Buildings with more than 10 stories
  • Healthcare buildings
  • Nursing homes

Please note that the standard does not apply to single-family or small multiple-family residences (i.e. duplexes).

Risk Management Process: Creating A Water Management Program

ASHRAE 188 calls for a water management program to be developed within every organization that falls within the scope of the standard. Below is a brief explanation of the minimal steps required to create a water management program;
  1. Establish a team responsible for evaluating the building water system and implementing a program to minimize risk.
  2. Illustrate the building water system, including in-depth descriptions and flow diagrams for each element of your water system.
  3. Establish areas of concern; those areas within your water system that show potential for high legionella growth.
  4. Establish control measures and limits, while deciding on how they will be routinely monitored.
  5. Develop methods for monitoring and the required corrective action in the event monitoring results vary.
  6. Ensure the system is running as designed and meets or exceeds objectives.
  7. Continuously document findings; this may require the creation of various review/analysis templates and checklists.
Please note that once the water management program is created it needs to be reviewed on a regular basis. Business demands may shift, causing a change in water requirements and a review of the program. Other factors, such as nearby construction projects and contaminated cooling towers, may require regular adjustments to your water management program.

*This is solely an overview of the standard, please ensure you read the full standard before proceeding with your legionella risk management program.

 Contact A Water Expert Today

​Looking to improve your water treatment efficiencies and reduce your water treatment costs? Contact our team of water experts to learn how the Vortisand® systems can help meet your water objectives!

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