Legionella: Your plumbing system’s silent killer

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Twelve dead and 113 reported cases in an ongoing Legionnaires’ disease outbreak in New York City that dates back to July 10. The culprit? The sneaky SOB incubated in cooling towers in more than a dozen areas.

LegionellaI recall asking, “Why? How?” at a recent “Pathogen Risk Reduction by Design” seminar hosted by Tim Keane in regard to Legionella and plumbing systems design. Tim is a consulting engineer and owner of Legionella Risk Management, Inc. he is also an original voting member of ASHRAE 188 committee serving on that committee for over a decade. How does this happen and why are recent plumbing code changes making this problem more likely rather than less likely to occur?

Legionella, for example, can cause debilitating, even deadly, results in elderly people and those with compromised immune systems, and cases of Legionnaires’ disease outbreaks are seldom reported and perhaps not seen as a global problem—until recently. “Ninety percent or more of those that get Legionnaires’ disease have risk factors,” says Keane (Risk factors include: age, over 50; smokers, drinkers, diabetes, organ transplants, HIV, and others.)

As a result of the recent New York outbreak, according to the USA Today, New York City Mayor Bill de Blasio said the proposal would require all existing cooling towers to be registered with the city’s Department of Buildings. It also requires regular inspection, testing, cleaning and disinfection. He said the city had created a voluntary online registration database for cooling towers.

“It’s hard to believe that plumbing code changes over the past decade have made plumbing systems more likely to be at risk for Legionella colonization. Of course, what’s happening in NYC, this prolonged outbreak and now the Governor stepping in and telling the NYC mayor that the State and CDC will be getting involved, that’s really hard to believe. A public health crisis and public health officials in the largest city in the U.S. being told things need to change. Maybe we should get the Governor involved in plumbing code changes,” says Keane.

But back to how, and why. The seminar, sponsored by Viega, the company dedicated to water quality solutions through innovative plumbing components, brought to light the importance of plumbing design in overall pathogen risk reduction and control. “Twenty-five percent of Legionnaire’s Disease outbreaks occur within the first year of new construction or renovation,” says Keane.

Legionella can also cause a less-severe influenza-like illness known as Pontiac Fever. Most cases of legionellosis are the result of exposure to Legionella associated with building water systems, according to ASHRAE presidential member Tom Watson, chair of the committee that wrote the 188 Standard (see more below).

Transmission of Legionella is the aerosolization and aspiration from an environmental source into the lungs and because it is chlorine tolerant, it can survive the water treatment process and pass into the water distribution system. It grows in the water systems in the right conditions, i.e. water temperature, sediment and commensal microbes.

According to OSHA guidelines, water operations and proper controls prevent Legionella amplification; it is important to remember that any water system can be a source of disease if the water in it is subjected to conditions that promote growth of the organism. Remember, however, that the primary sources of exposure to contaminated water are heat rejection systems—cooling towers, fluid coolers, etc.—and hot water systems. Maintain domestic water heaters at 140 F and water delivered at the faucet at a minimum of 122 F.

ASHRAE’s guidelines are “conditions that are favorable for the amplification of legionellae growth include water temperatures of 77 F – 108 F, stagnation, scale and sediment, biofilms and the presence of amoebae.”

Variables such as water flow, distribution, velocity and temperature and play an important part for risk reduction. Risk factors such as water supply, building use and size, system design and hot water set-up all contribute to a safe and effective plumbing system. “Potable water is biggest culprit for Legionnaire’s Disease,” said Keane.  There are more outbreaks of Legionnaires’ disease associated with potable water however potable water outbreaks tend to have few cases. Cooling tower outbreaks can be many times larger than a potable water outbreak.

Water Supply Risk Factors

• Supply Water Type — Surface water is a much higher risk than well  water
• Type of Disinfectant — Chlorine, Monochloramine
• Disinfectant Residual at Building — Distance building from treatment plant; city flushing plan; occupancy rates in area
• Potential for Water Disruption — Renovation, Failure

Building Risk Factors

• Building Use — Expected occupancy rate, Seasonal occupancy fluctuation, phased construction
• Building Size — Increased risk for buildings with more than 10 stories

Plumbing System Design

• Hot and Cold Water Pipe Runs — Insulation, location of runs, distance between hot and cold pipes, volume of stored water, parallel vs. series

“Keep water away from excessive heat sources such as cold water capturing heat from mechanicals or underwater lighting systems that can raise water temps,” says Keane.

• Hot Water Return — Balancing, return pumps, monitoring
• Turnover (Water Aging) — Balancing, flow rate (ft./sec.), volume of water in branches, unused distal sites

Hot Water Heater Setup

• Outlet Temperature
• HW return
• Master Mixing Valve Installation
• Series or Parallel
• Monitoring

ASHRAE Standard 188 is essential for anyone involved in design, construction, installation, commissioning, operation, maintenance, and service of centralized building water systems and components. “ASHRAE 188 will make and immediate impact in the healthcare industry, ” says Keane.

Specific requirements in the standard include:

• Minimum Legionellosis risk management requirements for the design, construction, commissioning, operation, maintenance, repair, replacement and expansion of new and existing buildings and their associated (potable and non-potable) water systems and components.

• Establishment by building owners of a Program Team and (in turn) a Water Management Program for which they are responsible in order to comply with the standard.

• Provision of specific and detailed requirements for what Legionellosis control strategies must accomplish and how they are to be documented – but, does not provide (or place restrictions on) what specific strategies are to be used or applied.

“With 8,000 to 10,000 cases of Legionnaires’ Disease reported each year in the United States, and with more than 10% of those cases fatal, it is vital that we set requirements to manage risk of this bacteria,” said Watson.


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