Legionella: Water Management Systems

May 20, 2019

In a previous blog post, Indoor Science covered The Basics of Legionella. Legionella is a bacterium that can be found naturally in various freshwater environments. This bacteria becomes a health hazard to people when it is inhaled. In this blog post, I will discuss where Legionella can be found in building water management systems, and how it is tested.

Legionella: Health Effects

Legionella bacteria are responsible for causing Legionnaires Disease and Pontiac fever. These are respiratory diseases that have pneumonia-like symptoms including fever, cough, and muscle aches. Typically, those at a higher risk of getting sick are the elderly, smokers, and people with weakened immune systems [note] https://www.cdc.gov/legionella/about/causes-transmission.html [/note]. Currently, a vaccine is not available that can prevent Legionnaires’ disease. According to the CDC, the cases of Legionnaires’ disease are increasing[note]https://www.cdc.gov/legionella/wmp/toolkit/index.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Flegionella%2Fwmptoolkit%2Findex.html[/note].

For the bacteria to be transmitted into the lungs, contaminated water must be aerosolized. The water contaminated with Legionella can come from various sources including hot tubs, decorative fountains, cooling towers, showerheads, and sink faucets. It is also worth mentioning that a typical home or car are at lower risk for Legionella growth because they do not use evaporative coolers in the air conditioning process [note] https://www.cdc.gov/legionella/about/causes-transmission.html [/note]. Also, the hot water piping systems of homes are generally less complex.

Legionella: Water Management Systems

To reduce the risk of contracting Legionnaires’ Disease, many large buildings implement a water management system. In general, this includes the following: an assessment of the building water systems, identify areas where Legionella growth is possible, determine when control measures should be implemented and how they should be monitored, determine a plan of action when control limits are not met, and ensure that the water management plan is running effectively [note]https://www.cdc.gov/legionella/wmp/toolkit/index.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Flegionella%2Fwmptoolkit%2Findex.html[/note]. The best water management plans, in my opinion, are those that require quality control testing of Legionella in the water. A company like Indoor Science can collect samples from the risky areas identified in the water management plan including cooling towers, water filters, decorative fountains, or from domestic water supplies.

Legionella: Causes

Building engineers should consider a few things when determining if there is potential for Legionella contamination. One of those is temperature. Legionella’s optimal temperature growth occurs between 77°F-108°F[note]https://www.cdc.gov/legionella/wmp/toolkit/index.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Flegionella%2Fwmptoolkit%2Findex.html[/note], with an ideal temperature around 100°F.  This makes temperature fluctuations in a building’s water system an important parameter to log. The presence of biofilm should also be monitored. Biofilm is basically slime that can adhere to different continuously damp surfaces.  Biofilm can harbor Legionella growth. Additionally, water pressure changes in pipes can dislodge biofilm from one area and move it down the plumbing system to a different area. Stagnant water can also lead to biofilm growth. Many water systems use disinfectants to prevent bacterial growth, however, they are most effective within a narrow pH range of 6.5 to 8.5 [note]https://www.cdc.gov/legionella/wmp/toolkit/index.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Flegionella%2Fwmptoolkit%2Findex.html[/note].  Therefore, changes in pH can render some disinfectants inadequate and allow Legionella to grow.  There are other factors that a building engineer must consider when determining if there is a potential for Legionella bacterial growth but these are a few more common problems. Any areas where water is warm, stagnant, and aerosolized are at high risk.


Much of the information about water management systems and Legionella in this blog post comes from the Center for Disease Control (CDC). They even have a tool kit to help buildings put together a water management plan. It is also worth noting that water samples collected for Legionella can be sent to a lab that follows a CDC method for analysis. A company like Indoor Science can be a great resource for building engineers when implementing a water sampling program.