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NYC Legionella water testing

Legionella Water Testing

Legionella testing is usually performed by collecting water and swab samples from the hot water distribution system in a building. 

Throughout New York City and Long Island, periodic water testing for Legionella bacteria in hospitals, retirement and nursing home facilities, schools, and hi-rise and low-rise apartment buildings has become the new norm as outbreaks continue to surface. Angstrom Testing Services has trained and experienced technicians that are able to properly evaluate whether your building’s potable water supply distribution system or cooling system may be sources of Legionella bacteria. 

If Legionella bacteria is found in sections of a water supply distribution system, then proper cleaning and disinfection of the system is necessary to eradicate the Legionella from the system. Angstrom Testing Services works with several licensed master plumbers that have successfully eliminated Legionella through recognized disinfection techniques with minimal disruption of services to building occupants. Call Angstrom testing Services LLC today to speak to one of our Legionella technicians. 

If necessary, we can meet with you and your staff and help your team prepare required maintenance plans for your facility.   Please don’t hesitate to contact us today.   For more information visit NYS Department of Health’s website.

Legionella Water sampling
Legionella Long Island map

About Legionella Testing

Legionella bacteria can colonize and spread throughout a building’s water distribution system and contaminate the drinking water supply. The bacteria proliferate in hot water and are circulated into the boiler and hot water tanks in closed loop and recirculated water systems during normal water use.

The species L. pneumophila is the most common Legionella bacteria and causes a pneumonia-type illness called Legionnaires’ disease. The bacteria may be consumed by building occupants by drinking and cooking with Legionella contaminated water and by inhaling steam and water mists during showering. 

Venerable populations include individuals with compomised immune systems, COPD, cardiomyopathy, emphysema, bronchitis, and older people, are most at risk and may acquire Legionella related lung infections, such as pneumonia. Complications and/or death may result from pulmonary edema (fluid build up in the lungs), reduced ventricular ejection fraction, and heart failure.

Cooling Towers

Cooling towers are water recirculating systems that remove excess heat from recirculating water. The recirculating water is used to absorb heat from a building’s air conditioning and mechanical systems, and the heat in the water is released into the air by aerosolizing the hot water into airborne mists and small droplets. Most of the mists and droplets condense and collect at the bottom of the tower, and the collected water is recirculated through the system. However, some of the mists and droplets are carried away in the outdoor air and have the potential to be inhaled.

Cooling tower legionella testing
Rooftop Cooling Tower

The hot water circulating through a building’s cooling tower plumbing system, air conditioning system, or mechanical system provides an ideal environment for Legionella bacteria to proliferate. Once the water in the cooling tower system is contaminated, the mists and aerosols that are formed in the tower during the heat exchange process provide ideal pathways for inhalation exposure to nearby building residents and workers. 

 

State and local municipal laws have been enacted and implemented that require cleaning, disinfection, and testing of the plumbing distribution system and cooling tower plumbing  components to demonstrate that Legionella are not proliferating within the tanks or systems and causing an exposure risk.  In New York City, local law 77 required cooling tower testing every 90 days.   

Key Requirements for Building Owners

  • Mandatory Registration: All towers must be registered with the NYS Cooling Tower Registry. If the building is in the five boroughs, it must also be registered with the NYC DOHMH portal.

  • NEW: 31-Day Sampling (NYC Only): As of May 7, 2026, Local Law 159 mandates that all NYC cooling towers be tested for Legionella culture every 31 days while in operation (previously every 90 days).

  • 90-Day Compliance Inspections: Every tower requires a technical inspection by a “Qualified Person” every 90 days to certify that the Maintenance Program and Plan (MPP) is being followed.

  • ASHRAE 188 Maintenance Plans: Every facility must have a site-specific written Maintenance Program and Plan (MPP) that is updated at least every three years.

  • Annual Certification: By November 1st of each year, owners must electronically certify that all required inspections, cleanings, and tests were completed.

  • Immediate Notification: Any Legionella culture result $\geq 1,000 \text{ CFU/mL}$ must be reported to the Department of Health within 24 hours.

System Disinfection to Control Legionella

A water system cleaning means disinfecting the whole water distribution system rather than just treating an isolated storage tank or a specific run of pipe work. There are two key ways of completing the disinfection process:

Thermal Disinfection 

Thermal disinfection uses heat to bring the water up to a very high temperature, high enough to quickly kill the Legionella bacteria. The taps and other outlets are then opened slightly to draw the water slowly through the entire system – flush.

Chemical Disinfection 

Chemical disinfection usually involves a biocide such as chlorine dioxide or hyper-chlorinated water solution, which is added at a controlled dose to the water system. To allow the disinfectant to reach every part of the plumbing distribution system, the taps and other outlets are opened slightly.  Outlets are then closed to allow the disinfectant to stagnate in the pipes and kill the bacteria. 

After a set period of time (usually 2 to 4 hours), a neutralising chemical agent is applied or the system is flushed to allow the disinfectant to clear the system. 

Retesting may be performed after positive test results are found. Retesting involves a waiting period of 7 to 10 days prior after the disinfection was performed. 

Contact us today at 516-724-4574 if you need a water disinfection specialist to eradicate Legionella  from your facility.

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Angstrom tested the water at each of the sinks in our daycare center for lead. They helped us get our license from the New York City Department of Health. They arrived on time and got the job done without any hassles and provided all the paperwork that I needed. Thanks again! Philip Bleeker

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