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In wake of Legionnaires' outbreaks, a debate over NYC's water and industry influence
By
Joe Hong
Published Oct 5, 2026 at 6:30 a.m. ET
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Yuriy Turetskiy/Getty Images
By
Joe Hong
Published Oct 5, 2026 at 6:30 a.m. ET
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A cascade of deadly outbreaks of Legionnaires' disease over the past two years has resurfaced an old question about how New York City manages its water supply. Should it build a mammoth, multibillion-dollar filtering plant for the billion gallons of drinking water that slosh into the five boroughs from the Catskill Mountains every day?
According to Bob Bowcock, a water management expert and board member of the Alliance to Prevent Legionnaires’ Disease, the answer is yes.
He recently argued to city officials that the water supply is a source of dangerous Legionella bacteria that can make its way into a building’s plumbing system, as well as rooftop cooling towers, which have been the subject of increased scrutiny and regulation because they’re capable of broadcasting Legionella into the air and causing an outbreak.
“Cooling tower regulation alone is not comprehensive Legionnaires disease prevention,” Bowcock told members of the City Council’s health committee in September, arguing that Legionella bacteria in drinking water is contaminating buildings and cooling equipment. “The water in the tower is the same water that runs through the entire system.”
Rising temperatures and increased rainfall are driving an uptick in the number of Legionnaires' infections, according to several studies. And it’s left scientists with many unknowns about how Legionella is growing and spreading in the built environment, said Annette Davison, an Australia-based water systems expert who is not affiliated with the alliance and does not advocate for filtration.
“Because of climate change in particular, our systems are going to be changing,” Davison said.
City officials point to past studies that show only low levels of Legionella in the city’s water supply and insist filtering is unnecessary because the bacteria is not at quantities that would pose a public health threat. And to Bowcock’s opponents, the alliance he represents is nothing more than a nonprofit front for a cooling tower industry that would like to deflect lawmakers’ attention away from the role its products play in outbreaks.
“They have concerns that the focus on cooling towers will hurt their business,” said Janet Stout, a leading expert on Legionella and cooling towers. She said filtering the city’s water would be costly and do little to prevent future outbreaks, and she criticized the alliance for influencing regulations in other states that placed more responsibility on water utilities. She said cooling towers are the main cause of outbreaks and that public health departments should maintain a focus on them.
Tax filings show the Alliance to Prevent Legionnaires’ Disease is a who’s who of cooling tower manufacturers. Over the past 10 years, its board has included executives from the largest cooling tower manufacturers in the country, including Don Fetzer, president of Baltimore Aircoil Company; William Bartley, president of Evapco; and Kenneth Mortenson, a manager of research and development at SPX Cooling Technologies.
The group has long argued that the city is too narrowly focused on cooling towers, advocating instead for what it calls a “source to tap” approach that treats and monitors Legionella levels in drinking water. Eight years ago, as city lawmakers were weighing how to strengthen inspection requirements, the alliance’s director of technology and science, Daryn Cline, testified before the City Council.
“Equipment-focused requirements will not address New York City’s [Legionnaires’ disease] issues,” Cline told officials at the 2018 hearing. “Filter all the city water.”
While he acknowledged under the Council's questioning that the alliance was founded by cooling equipment companies, he did not disclose that he is also a longtime Evapco executive.
Cline, Fetzer and Mortenson did not immediately respond to a request for comment.
Bartley, Evapco’s president and a founding board member of the organization, said Stout and other water consultants in favor of stringent cooling tower regulations have their own financial interests, especially regular testing requirements.
Stout was the founder of Special Pathogens Technology, a lab that conducts Legionella testing. City records show the company has over $2 million in contracts as of 2026 to provide Legionella testing services for the city’s health department. Stout said she sold the company in 2021 and has advocated for Legionella testing, long before she started the lab.
Bob Bowcock, Alliance to Prevent Legionnaires' Disease
New York City Council
More recently, some members of the Alliance to Prevent Legionnaires’ Disease, including Bowcock, have applauded the city’s strict rules for cooling towers while continuing to push for filtration. Bill McQuade, a global vice president at Baltimore Aircoil Company, is also the former president of the American Society of Heating Refrigerating and Air-Conditioning Engineers, or ASHRAE, which has become an authority in cooling tower regulations. New York City’s own health code is based on ASHRAE’s standards.
“No matter how stringent they are on the regulations in New York City on cooling towers, they’re going to continue to have recurring outbreaks,” McQuade said in an interview with Gothamist. He also testified at the City Council health committee’s hearing in September.
It’s unclear how much traction his arguments have had with local lawmakers. Samie New, a spokesperson for Health Committee Chair Lynn Schulman, said the committee is still reviewing alliance members’ testimony and declined to answer questions about enhanced enforcement of building water systems and the possibility of filtering the city’s tap water.
Unfiltered system
New York City has the nation’s largest unfiltered water supply system. Most of the city’s drinking water comes from 19 reservoirs and three lakes upstate and surrounding the Hudson Valley. To protect this vast drinking water supply, the city’s Department of Environmental Protection has used a strategy of purchasing property that surrounds watersheds in the Catskill Mountains and implementing strict land-use restrictions. The federal government has waived a filtration requirement for the city ever since the federal regulations first went into place 23 years ago.
The city does filter some of its water. The Croton Filtration Plant, located in the Bronx, began operating in 2015. Up to 30% of the city’s water supply on a given day arrives through the plant from the Croton Watershed east of the Hudson River.
Douglas Auer, a DEP spokesperson, said all of the city’s drinking water is treated with UV radiation and chlorine. The water is also tested for Cryptosporidium and Giardia, two pathogens that cause intestinal illness.
While the agency does not regularly test for Legionella, Auer said a 2022 study by the agency found Legionella levels are not high enough to be a public health threat.
Auer said an additional filtration plant would not help prevent outbreaks of Legionnaires’ disease. And Davison, the Australian water systems expert, said said there’s not enough evidence to justify the hefty price tag of filtration for taxpayers.
But she said more testing and monitoring is needed at every stage of any municipality’s water supply: at natural sources such as reservoirs, where water enters a city and the point it enters a building’s plumbing.
“We need to refocus our efforts,” she said.
City Council Health Committee Chair Lynn Schulman
Gerardo Romo / NYC Council Media Unit
The New York State Department of Environmental Conservation estimates that a filtration plant would cost between $8 billion and $10 billion to construct and $1 million a day to maintain. The Croton plant cost $3.5 billion to build, more than three-and-a-half times more than initial estimates.
But the Alliance to Prevent Legionnaires’ disease says the daunting price tag is worth it to battle the growing threat of Legionnaires’ disease.
In New York City, the number of Legionnaires’ cases more than doubled in 2025, hitting a 10-year record high with 657 cases reported, according to city health department data.
Last year’s high was only partly fueled by an outbreak in Central Harlem that sickened 118 people and killed seven. Even without the outbreak, the number of infections more than doubled from the 258 cases in 2024.
Case numbers have also climbed nationally over the past 20 years. The rate of infection has almost quadrupled. In 2005 the CDC estimated that fewer than one in 100,000 Americans were diagnosed with Legionnaires’ disease. In 2025, it was close to three per 100,000 people.
Experts attribute the rise in cases to a variety of factors. Climate change and rising temperatures allow Legionella to thrive. Aging infrastructure is harder to clean and disinfect, making it more vulnerable to contamination. And an aging population both in New York City and nationally is more likely to get severely ill from Legionnaires’ disease.
Chantal Gomez, a spokesperson for the health department, said 16 to 18 cases a year are connected to smaller clusters within buildings where people inhale mist from showerheads or faucets.
The vast majority of Legionnaire’s cases are not investigated because they aren’t connected to a larger outbreak or a shared water source.
For the Alliance to Prevent Legionnaires’ Disease, the increase in cases – and the fact that health officials don’t know the source of most infections – suggests that cooling tower regulations are not working and that the city should pay more attention to drinking water.
Bowcock said the group hired a water scientist to collect over 100 samples from hose bibs, faucets and outdoor fountains on the Upper East Side during the outbreak this summer. Test results showed that about 20% of samples had high levels of Legionella, he said.
Cooling towers on a building in Manhattan.
Caroline Lewis
Bowcock told lawmakers in September that Legionella in the water is contaminating cooling towers and indoor plumbing.
“Until we take a concentrated approach that's systematic, that goes from source to tap, we're going to continue to be back here year after year,” Bowcock said at the hearing.
But Chris Boyd, a water consultant and former health official who authored New York City’s cooling tower regulations, said it’s impossible to draw any conclusions about the city’s tap water from the alliance’s samples because the water could have run through the buildings’ plumbing before it was collected for testing.
Boyd said other researchers have drawn thousands of samples from a variety of water supply systems across several cities.
“What they’ve found uniformly across many studies is that there is no evidence that there is systemic risk of Legionella in municipal water systems,” Boyd said.
Boyd does agree with one of the alliance’s suggestions, however. It has proposed that the city require property owners create more comprehensive water management plans, detailing how they would test all water circulating in their buildings for Legionella and treat it when levels are high. Opposite of New Jersey and Los Angeles, current city regulations only require management plans for cooling towers.
Boyd said he also supports testing reservoirs after seasonal changes, like a heavy rain, which could lead to an uptick of bacteria and organic material in the water supply. But he said filtration is wasteful and unnecessary and that testing the water in buildings is a more strategic middle ground.
“That is where conditions to amplify [Legionella] exist,” he said. “There is no harm in increasing surveillance sampling.”
Joe Hong
Joe Hong is the investigative data reporter for WNYC and Gothamist. He previously covered K-12 education for several newsrooms across California. His reporting has led to local reforms in juvenile justice system as well as a state law requiring universal screening for dyslexia. Got a tip? Email [email protected]
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