Mitigating the Spread of Legionella in Water Supply Systems

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As buildings continue to reopen following pandemic-mandated shutdowns, the CDC has identified the possibility of increased cases of Legionella. This is the result of stagnant or standing water in a building’s unused or underused plumbing system, which allows Legionella and other biofilm-associated bacteria to grow and spread. 

Consequently, Legionella bacteria has become a serious concern for the plumbing industry and should be proactively addressed to ensure the health and safety of building occupants. 

What is Legionella? 

Source: CDC

According to the CDC, Legionella is a type of bacteria that lives in freshwater environments, but it can also grow in human-made settings where the water system is not maintained. Breathing in water droplets that contain Legionella bacteria can cause Legionnaires’ disease, an intense strain of pneumonia primarily affecting individuals above the age of 50 with weaker immune systems. 

The first case of Legionnaires’ disease was discovered in a Philadelphia hotel during the U.S. Bicentennial Convention of The American Legion in 1976, when the hotel’s water supply became contaminated with Legionella and spread among the hotel occupants. 

“Although we’ve seen more cases of Legionnaires’ outbreaks in multifamily residential settings and hotels, it can still be a threat anywhere a water heater is involved,” said Brian Helms, training manager at Charlotte Pipe and Foundry. 

According to the CDC, the most likely sources of Legionella infection include: 

  • Water used for showering (potable water)
  • Cooling towers (parts of large air-conditioning systems) 
  • Decorative fountains
  • Hot tubs
Although we’ve seen more cases in multifamily residential settings, Legionella bacteria can still be a threat anywhere a water heater is involved. Brian Helms Training Manager

Legionella Contamination Risk Factors 

When it comes to the spread of Legionella bacteria in plumbing systems, there are two critical components within the system to consider. 

Pipe Walls

In both domestic plumbing systems and multifamily residential systems, rigid pipe walls can create an environment for biofilm to rapidly develop. When pipe walls are rough, there is more of a risk for biofilm to cling to the inside of the piping and promote the growth of Legionella colonies. 

According to Legionella Control Systems, hard water scaling is a major attributing factor for Legionella growth because it protects harmful pathogens from being impacted by disinfectants and high temperatures. 

The graphic below illustrates how biofilm attaches and matures over time, creating more space for bacteria to multiply. 

Source: Legionella Control Systems

Water Heaters 

Accelerated by lukewarm water temperatures ranging from 68 F to 122 F, Legionella bacteria can thrive in water storage tanks. The temperature at which the bacteria populates is not an exact science, however, and makes it difficult to pinpoint the optimal temperature to maintain. If water storage temperatures fluctuate, especially to a lower range, there’s more of a risk for Legionella bacteria growth. 

The chart below outlines the temperatures where Legionella bacteria flourishes. 

Source: Lubrizol

5 Tips to Help Lower the Risk of Water Supply Contamination  

  1. Maintain water storage temperatures: As noted in the chart above, Legionella cannot survive when the water temperature is above 140 F. Water heaters should be set to deliver water consistently at or above 140 F, with measures taken to prevent scalding
  2. Consider tankless water heaters: Becoming more widely used in the plumbing industry, tankless water heaters are a solution to Legionella growth. Simply put, when there isn’t a tank to contaminate, there’s less risk of contamination. 
  3. Plan for pipe inspection: While there isn’t an evidence-based recommendation for testing water systems for potential contamination — and while outbreaks of Legionnaires’ disease are difficult to identify — facility management teams should consider ways to regularly monitor the health of the water supply system. 
  4. Avoid water stagnation: During periods of little to no water usage in a building — such as, say, a global pandemic — it’s important to thoroughly flush the system to promote the flow of fresh, healthy water for building occupants. 
  5. Identify less rigid plumbing materials: Overall, the solution to preventing Legionnaires’ disease is to stop it at its source: the plumbing system. Choosing the right water delivery pipes will safeguard the system as a whole. 

How Corzan® and FlowGuard Gold® Combat the Spread of Legionella

Manufactured by Charlotte Pipe, Corzan CPVC Schedule 80 and FlowGuard Gold CPVC CTS are less likely to create breeding grounds for bacteria in water supply systems. A 1999 study “Biofilm Formation Potential of Pipe Materials in internal installations, KIWA 1999” found that CPVC systems experience significantly less biofilm growth as compared to other systems. In part, this is attributed to the roughness of the pipe wall. Materials with a smoother wall surface are less prone to biofilm growth. Both Corzan and FlowGuard Gold are engineered with high levels of chlorine and are inherently corrosion resistant, creating a smooth interior pipe surface that helps prevent the pipe from becoming a biofilm-friendly environment. 

With less risk for system degradation, high temperature capability, and greater resistance to disinfectants like chlorine and chloramine, buildings with Corzan and FlowGuard Gold are equipped to last longer with less maintenance than other piping materials.

Charlotte Pipe actively educates its stakeholders and associates on the dangers of Legionella while seeking new information on the topic. To understand the safest, most effective pipe material for your plumbing system, contact the Charlotte Pipe Technical Support team and learn more about putting safety first in plumbing design

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