NYC Legionella Compliance - Local Law 77 & Local Law 159
If you own or manage a building in New York City with a cooling tower, Legionella compliance is no longer optional — and the rules just got significantly stricter. Local Law 159 of 2025, passed following a deadly outbreak in Central Harlem that killed seven people, mandates monthly Legionella testing starting May 7, 2026, with civil penalties starting at $10,000 per violation. Acqua Treat has been guiding NYC building owners through cooling tower compliance since 1982. Here is what you need to know, and how we can help.
If you also need a chemical water treatment program for your cooling tower, see our Cooling Tower Water Treatment page.
What Changed — Local Law 159 of 2025
In 2025, New York City passed Local Law 159 — the most significant update to cooling tower regulations since Local Law 77 was enacted in 2015. Key changes:
Your cooling tower is now considered “in operation” as soon as it has been filled or partially filled with water
Legionella testing now required every 31 days (monthly), replacing the previous 90-day requirement, by an ELAP-certified laboratory
NYC DOHMH must be notified electronically within 5 days of start-up or shut-down
Tightened Legionella sampling window now 3-14 days following hyperhalogenation
Failure to provide required records upon request is now considered prima facie evidence that the records do not exist and the corresponding requirements were not satisfied
Records must be displayable on a digital device (computer or tablet) at the time of inspection and available in standard formats such as PDF
Fines are increased across the board, with most penalties doubled
Enforcement begins May 7, 2026
What's Still Required Under Local Law 77
Local Law 159 adds to Local Law 77 — it does not replace it. All existing requirements remain in force:
Cooling tower registration with NYC DOHMH through the Cooling Tower Registration Portal
A current Maintenance Program and Plan (MPP) developed by a qualified person
Legionella sampling every 90 days (increasing to monthly under LL159 from May 2026)
Weekly heterotrophic bacteria monitoring
Daily water treatment records — pH, conductivity, biocide levels
Cooling tower cleaned and disinfected at least twice per year
Annual certification submitted to the portal by November 1
All records retained for a minimum of three years
Immediate DOHMH notification within 24 hours if Legionella results reach 1,000 CFU/ml or above
Our Legionella Compliance Services
Acqua Treat provides full-service Legionella compliance support for cooling towers across New York City, including:
Monthly Legionella sampling and testing through an ELAP-certified laboratory — compliant with Local Law 159
Development and maintenance of your Maintenance Program and Plan (MPP)
Quarterly and annual compliance inspections by qualified personnel
Cooling tower cleaning and disinfection, including summertime hyperhalogenation
Emergency disinfection services for failed Legionella tests
DOHMH reporting and documentation support
Annual certification preparation and filing
Water Management Plan (WMP) development per ASHRAE Standard 188
Consequences of Non-Compliance
The consequences of non-compliance have escalated significantly under Local Law 159:
Fines starting at $1,000 per violation under the new law
Misdemeanor charges for failure to disinfect a tower with elevated bacteria levels
DOHMH-ordered cooling tower shutdown during high-risk periods
Civil liability exposure if a Legionella outbreak is traced to your building
Open violations can block property sales, refinancing, and certificates of occupancy
If you have received an Inspection Summary Report (ISR) or Violation Deficiency Report (VDR) from the NYC Department of Health, contact us immediately. We can help you understand the findings and develop a corrective action plan.
The changes required - restructuring your testing schedule, switching to an ELAP-certified lab, updating your MPP - take time to put in place correctly. Contact Acqua Treat today for a free compliance review!