How can Legionella Growth be Prevented?

Legionella bacteria occurs naturally in water such as lakes and rivers. It also has the potential to grow in water systems that the public is exposed to. This bacteria does not affect most healthy people, however the elderly, those with weakened immune system and smokers are at higher risk for contracting a lung infection called Legionnaries’ disease (LD) from the bacteria. Preventing Legionella bacteria from growing and multiplying in plumbing and water systems is key to reducing the risk of contracting LD.

Legionella bacteria has the ability to colonize in man-made water systems which often support an ideal environment and temperature for the bacteria to grow. Legionella bacteria have an optimum growth temperature of between 95 and 115 degrees F., an optimum pH of between 5.0 and 8.5, and often flourish inside scale and sediment. Conventional water and air conditioning methods used in recirculating cooling towers, air conditioning, humidifiers, water storage, aquatic systems as well as hot and cold domestic water systems harbour Legionella and cause the potential for the bacteria to become hazardous to a large number of people.

Active prevention is key to minimizing the possibility of Legionella in water systems. For every water system, there should be a risk assessment, followed by the development of standard operating procedures and a written maintenance plan. A knowledgeable staff member should administer a water test once a month. Here is an example of how to properly take a water sample. First it is important to wash your hands thoroughly with soap and water. Next, turn on the faucet water and let it run for 2 - 3 minutes until the water is warm but not hot. The goal is to obtain water currently in the distribution system. Avoid heating water excessively. Fill the sample bottle provided with water until it reaches the indicated line. Also avoid over filling the sample bottle. Put the top on the bottle and tighten to prevent leaking. Insert the sample into the package provided along with the ice pack and mail it back to the water lab for immediate testing. The water will then be tested in the lab and findings will be reported. If the water tests positive for the bacteria, treatment options and instructions will be provided and additional testing will be required.

When it is suspected that the water is contaminated with Legionella, an investigation should be done that consists of an overview of the building water systems via a walkthrough, an identification of components that may present risk, and any recent changes in the system. Water temperatures and the condition of the systems should both be assessed. OSHA has published a two-level approach to diagnosing and treating water in the water systems which can be accessed on their website at

Legionella can pose serious problems when present in water systems. It is the responsibility of the building administration to implement a protocol that regularly tests for bacteria in the water, cleans the system and is prepared to take action if Legionella is identified. Prevention is the key to minimizing the risk of spreading Legionnaires’ Disease.

Active prevention is key to minimizing the possibility of Legionella in water systems.
Implement Your WMP Today

The Legionella Watch Water Management Program (WMP) helps your facility to satisfy the requirements set forth by the CMS, including the implementation of regular water testing protocols with documented results, education on proper water collection methods, and more.