New York City Local Law 159: What Monthly Legionella Testing Means for Your Cooling Tower Program

In 2015, a cooling tower outbreak in the South Bronx killed 12 people and sickened well over 100 more, prompting New York City to pass the nation’s first law mandating Legionella testing for cooling towers. That law required quarterly testing — a cadence that held for a decade, even as questions persisted about whether it was frequent enough.

Those questions became urgent again in 2025, when a community cluster of Legionnaires’ disease in Central Harlem led to 118 confirmed cases, 92 hospitalizations, and 7 deaths. In response, the New York City Council and the NYC Health Department moved to strengthen the city’s cooling tower law. On May 8, 2026, those changes took effect.

If your building has a registered cooling tower in New York City, here’s what Local Law 159 means for you and how to get your compliance program ready.

What’s Changed Under Local Law 159?

Local Law 159 of 2025, along with the Health Department’s conforming amendments to Chapter 8 of Title 24 of the Rules of the City of New York, took effect May 8, 2026, and apply to the thousands of buildings across the five boroughs with registered cooling tower equipment.

Local Law 159 doesn’t replace Local Law 77; it amends it, raising the bar on several core requirements, most notably testing frequency. Previously, building owners had to test their cooling towers for Legionella at least once every 90 days while the system was operating. Now that interval drops to no more than 31 days between samples, effectively tripling the required testing frequency.

While testing frequency often draws the most attention, Local law 159 touches several other parts of a compliant cooling tower program:

Lab certification and documentation. Every Legionella culture analysis must be performed by a laboratory certified under the New York State Environmental Laboratory Approval Program (ELAP).

Annual plan certification. A qualified person must certify the building’s Maintenance Program and Plan every year.

Valve schedule and flow conditions. Maintenance Program and Plans now need to include a valve schedule and specifically address low-flow and no-flow conditions.

Faster shutdown/startup reporting. Building owners must notify the Health Department electronically within 5 days of any cooling tower shutdown or startup.

Operation period reporting. Owners must designate and report the system’s operation period through the required registration/reporting process.

Higher penalties. Fines for noncompliance have increased across the board, with new penalties applied for failing to meet reporting requirements.

These changes build on requirements that remain in place, including compliance inspections by a qualified person at least every 90 days and the Annual Certification of Compliance, due through the NYC Health Department’s cooling tower registry by November 1 each year.

What These Changes Mean for Your Compliance Calendar

 Taken together, these requirements turn Legionella compliance from a periodic task into a standing operational rhythm. The 90-day cadence gave building owners a comfortable margin: a late sample or slow lab turnaround rarely put compliance at risk. A 31-day cadence offers no such cushion. Miss the window by even a few days, and what used to be a scheduling inconvenience becomes a compliance gap.

That makes a reliable testing routine essential. It isn’t just a sampling date on the calendar, but a dependable cycle of collection, lab turnaround, and results review that holds up month after month. It also raises the stakes in choosing a lab. With thousands of cooling towers citywide on a 31-day testing schedule, your laboratory partner needs the capacity to handle that volume, the ELAP accreditation the law requires for culture analysis, and turnaround fast enough to keep both your results and your next sample on schedule.

A New Outbreak Exposes Low Compliance, Prompting Increased Enforcement

Local Law 159 had been effective for barely two months before it faced its first real test. In early July 2026, a new Legionnaires’ disease cluster emerged on Manhattan’s Upper East Side. By the time the city declared the exposure risk over on July 31, the outbreak had sickened 92 people and killed 7. The toll kept climbing afterward, reaching 94 cases and 11 deaths by late August, as investigators continued to search for the source.

What made the outbreak notable wasn’t just its timing — it was what data revealed about compliance with the very law meant to prevent it. An analysis of the NYC cooling tower registration portal found that as of early July, only about 14% of building owners citywide had submitted a Legionella test sample since the monthly testing requirement became enforceable on May 8. A decade of inspections under the original law had already produced a 70% violation rate across more than 123,000 inspections, with roughly 1 in 10 inspections turning up a Legionella-specific public health hazard — no maintenance program, no testing records, or documented failure to follow up on elevated results.

In response, the city ramped up enforcement, conducting roughly 800 field inspections citywide since May, issuing more than 110 summonses in the outbreak area, and publicly releasing the addresses of buildings whose cooling towers screened positive.

The Pressure Isn’t Letting Up

Local Law 159 and the enforcement push that followed the Upper East Side outbreak aren’t the end of the story. On August 5, 2026, Governor Hochul signed Chapter 206, a new state law aimed at New York City cooling towers. It adds twice-yearly owner or operator certifications, faster response requirements for certain microbial test results, 10-year record retention, and higher civil penalties. The response and remediation deadlines took effect in early September, and the rest of the law takes effect in early November.

Then in September, the NYC Health Department began investigating a new community cluster in the South Bronx. As of September 20, it had grown to 21 cases and two deaths. Notably, nearly all the registered towers in the original affected ZIP codes had submitted test samples, a reminder that sampling is only part of the job. Results have to be reviewed and elevated counts acted on quickly.

An Action Checklist for New York City Facility Managers

Local Law 159’s accelerated testing cadence and the city’s renewed commitment to enforcement leave little room for error. The steps below will help you set up a program that keeps you on schedule and holds up to closer scrutiny.

• Confirm your Legionella testing lab is NYS ELAP-certified and can consistently return results within your sampling window
• Update your Maintenance Program and Plan to include a valve schedule and address low-flow/no-flow conditions
• Rebuild your sampling calendar around a 31-day (not 90-day) interval, with buffer for holidays, lab turnaround, and staffing gaps
• Establish a workflow for electronic 5-day notification of any tower shutdown or startup
• Schedule annual plan certification by a qualified person well ahead of your registry deadline
• Review your registration to confirm your reported operation period is current

Local Legionella Testing You Can Trust

Pace® supports New York building owners with a local presence backed by a nationwide network. With three laboratories in New York State and a service center in Manhattan, we’re positioned to help you meet the demands of the 31-day testing cycle.

Our Legionella testing network includes NYS ELAP-certified, CDC ELITE-participating, and AIHA-accredited locations with the capacity to deliver the fast turnaround monthly testing requires. In addition, we offer Water Management Planning services that can help you update your Maintenance Program and Plan to meet Local Law 159 documentation requirements. If a positive result calls for immediate action, our Legionella Emergency Response Services can help you respond—swiftly and appropriately.

If you manage cooling towers in New York City, now is the time to confirm your program meets the new requirements. Contact our Legionella team today.

Related Reading:

Averting Tragedy: Testing Cooling Towers for Legionella

Should You Test for Legionella?

What Facilities Managers Need to Know About New Jersey’s New “Legionella Law”