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Five Ways to Thwart Legionnaires' Disease

Reported cases of Legionnaires’ disease in the South Bronx, NY, have climbed to 119, with 12 adults dying after exposure. As NYC officials continue to monitor the outbreak and building owners and managers double down to disinfect affected sites, Healthy Buildings VP and Northeast regional manager Dean Tyler suggests ways to mitigate risk.


Increase domestic hot water temperature: The Legionella bacteria is often found in water sources, but it thrives in the 95°F to 115°F range, says Dean, whose firm assists owners and property managers with water, air quality and energy monitoring and prevention. Increase the temperature of the water so the discharge temperature is above 120°F.

Make sure cooling towers are clean: While the chemicals to disinfect cooling towers do help kill the bacteria, entire eradication is difficult if there is sediment, rust, scale or biofilm present. “It’s imperative to keep them as clean as possible,” he urges. A total flush of a tower may be the only way to achieve this, although it’s difficult when the systems run 24/7.

Prevent stagnation: Standing water is a breeding ground—make sure there’s no opportunity for the bacteria to flourish. One problem area is in buildings that have upgraded to waterless urinals, he notes; often, there is leftover pipe (called a “dead leg”) left from previous flush urinals that can harbor stagnated water and send it back into the recirculating system.


Above is the NYC Department of Education building at the former Samuel Gompers High School, one of the 20 sites in the South Bronx that have tested positive and have been or are being decontaminated.

Develop a water management plan: Last month, ASHRAE released Standard 188 to help curb Legionnaires outbreaks, and Dean predicts that over the next couple of years, we’ll see it adopted as code. It encourages developing schematics that look at building water distribution, plumbing diagrams, eliminating dead legs and how to address your systems during maintenance.

Educate your tenants: There’s a lot of misinformation about Legionnaires, Dean says; two of the most common are that you can catch it by drinking water or by being infected by another person. The fact is that people only get sick by breathing in water vapor containing the bacteria, he says. (Mayo Clinic offers up-to-date info on symptoms and treatment.)