NYC Cooling Towers Face New Monthly Legionella Testing Requirement in 2026
Beginning May 7, 2026, cooling tower owners in New York City will need to comply with a new testing requirement under Local Law 159 of 2025. The law updates the New York City Health Code to require monthly Legionella culture testing for cooling towers during operating months.
This change significantly increases testing frequency compared to current requirements and is intended to strengthen oversight of cooling tower maintenance and reduce the risk of Legionella outbreaks.
What Is Changing?
Currently, cooling towers must be sampled for Legionella within 14 days of seasonal startup and at least every 90 days during operation under guidance from the New York State Department of Health.
Under the new NYC requirement:
- Cooling towers in NYC: Sampling required every 30 days (monthly) during operation
- Cooling towers outside NYC (rest of New York State): Continue 90-day (quarterly) sampling
The rule also clarifies that no more than 31 days may pass between samples.
For many facilities, this means increasing Legionella testing from four tests per year to as many as twelve annually.
Other Requirements Remain in Place
While Legionella culture testing frequency is increasing, several existing requirements remain unchanged:
- Weekly monitoring using Heterotrophic Plate Count (HPC)
- Sampling within 14 days of seasonal startup
- Compliance with action thresholds established by the New York State Department of Health
Cooling tower owners must also submit their Annual Certification of Compliance through the NYC Department of Health and Mental Hygiene cooling tower registry by November 1 each year.
Local Law 159 also introduces preventative warm-weather disinfection requirements, typically during the peak summer months when Legionella growth risk is highest.
Why the Change?
The increased sampling frequency is intended to:
- Improve early detection of Legionella growth
- Reduce the likelihood of Legionnaires’ disease outbreaks
- Strengthen oversight of cooling tower maintenance and water treatment programs
How Eurofins Built Environment Testing Can Help
With NYC cooling tower testing frequency increasing threefold, Eurofins Built Environment Testing is ready to support NYC cooling tower owners and water treatment providers through:
- Local NYC Service Center for convenient sample drop-off
- Dedicated courier logistics across the NYC metro area
- ELAP-certified Legionella culture testing
- Legionella testing media and sample kits
- Advanced rapid detection tools including PCR
- Regulatory guidance to help facilities prepare for the transition
Preparing for the New Requirement
Cooling tower owners should begin preparing now by:
- Identifying cooling towers located in NYC
- Updating sampling schedules to monthly testing
- Planning for increased testing volume
- Confirming laboratory certification and reporting capabilities
Prepare for the new NYC testing requirements with confidence. Contact Eurofins Built Environment Testing today to schedule Legionella testing, request sample kits, or speak with our experts about building a compliant cooling tower monitoring program ahead of the May 2026 deadline.