NJ Department of Health, Hamilton Twp. Officials say Water is Safe to Drink, But Urge Precautions During Ongoing Legionnaires’ Disease Investigation

September 22, 2021

HAMILTON TOWNSHIP, NJ (MERCER)–Four cases of Legionnaires’ disease were reported in Hamilton Township, Mercer County between May-August 2021, along with an additional reported case from November 2020. The Hamilton Township Division of Health continues to work closely with the New Jersey Department of Health (NJDOH) to investigate these cases as part of a larger investigation, which was initiated in August 2020 following a reported cluster of four cases. Hamilton Township reported two deaths in August 2020 and an additional death was reported late last month in an elderly township resident among the nine reported cases.

Legionnaires’ disease is a type of pneumonia that people can get after breathing in aerosolized water (small droplets of water in the air) containing Legionella bacteria. Symptoms of Legionnaires’ disease include cough, shortness of breath, fever, muscle aches, and headaches which are similar to symptoms caused by other respiratory infections, including COVID-19. Most healthy people exposed to Legionella do not become ill. However, people who are 50 years or older, especially those who smoke cigarettes, or those with certain medical conditions, including weakened immune systems, chronic lung disease or other chronic health conditions, are at increased risk for Legionnaires’ disease.

Legionnaires’ disease is treatable with antibiotics so it is important that anyone who thinks they have symptoms of Legionnaires’ disease contact their health care provider and seek medical evaluation. Healthcare providers use chest x-rays or physical exams to check for pneumonia. Your provider may also order tests on a sample of urine and sputum (phlegm) to see if your lung infection is caused by Legionella bacteria.

Health officials are urging residents and business owners in Hamilton Township to take actions to reduce the risk of Legionella growth in their household and building plumbing. Recommendations for homeowners and building owners are available below. It can be possible for Legionella to enter buildings (including homes) when receiving treated drinking water. Health officials are partnering with NJ Department of Environmental Protection (NJDEP) and Trenton Water Works (TWW) to monitor for Legionella in the Hamilton Township water distribution system owned and operated by TWW. While water samples collected at TWW treatment plant and central pumping station have consistently shown no presence of Legionella, water samples collected from homes and businesses in Hamilton Township served by TWW, have identified the presence of Legionella. There is concern that Legionella may be present in other buildings and homes in the area. 

“The water is safe to drink, but there are basic precautions that residents can take to help protect themselves – such as regularly flushing water at their taps and maintaining their hot water tank,” said State Epidemiologist Dr. Tina Tan. “Additionally, home A/C units do not use water to cool, so these home units do not aerosolize water and are not a risk for Legionella growth.”

“We continue to work with our partners at the New Jersey Department of Health and Hamilton Township to empower residents in Hamilton and in our service area on how to protect themselves and their families from Legionnaires’ disease,” said Mark A. Lavenberg, Director of the City of Trenton’s Department of Water and Sewer, which operates Trenton Water Works. “To that end, starting on October 1, Trenton Water Works is launching a public awareness campaign to educate our service-area consumers on this critical public health issue.”

Hamilton Township Division of Health and NJDOH want to remind healthcare providers to maintain a high index of suspicion for Legionnaires’ disease when evaluating patients for community-acquired and healthcare-associated pneumonia, especially among residents of Hamilton Township. This is important to ensure patients receive appropriate and timely treatment.

“I want to thank NJDEP and NJDOH for their involvement in studying the frustrating frequency of Legionnaires’ disease cases in Hamilton over the past decade and working with TWW and our Division of Health to keep the residents of Hamilton safe,” said Mayor Jeff Martin. “Clean and safe drinking water is a human right – one that we will continue to fight to make sure all residents can comfortably know they have access to.” 


According to NJDOH, residents can follow recommended best practices to reduce Legionella growth in their household water. For more information on best practices, please visit NJDOH’s Legionella webpage at: https://www.nj.gov/health/cd/topics/legion.shtml

  • Let your faucets and showers run for at least 3 minutes when they have been out of use for more than a week. Care should be taken to minimize exposure to splashing and aerosol generation, for example, leaving the room while the water is running.
  •  Thoroughly clean or replace your shower heads and faucet aerators (screens) 3–4 times per year. To disinfect, use a 1:100 diluted solution of regular household bleach (1/4 cup bleach to 1 gallon of water). For concentrated bleach use 3 tablespoons for 1 gallon. Follow instructions found on the back of the bottle for safe use including only using disinfection products in a ventilated area.
  • Drain and flush your hot water tank every 6–12 months. Consider hiring a licensed plumbing professional to perform this.
  •  Clean and/or replace all water filters per manufacturer instructions, such as whole house (e.g., water softeners) and point-of-use filters (e.g., built-in refrigerator filters).
  • Remove, shorten, and/or regularly flush existing dead legs (a section of pipe capped off with little to no water flow). For future renovations, ensure your plumber avoids creating dead legs.
  •  Keep your hot water tank set to a minimum of 120°F. This temperature will reduce Legionella growth while minimizing risk of hot water burns. Higher temperatures can further reduce the risk of Legionella growth, but you should first install a mixing valve to prevent hot water burns when using the water. Check with manufacturer recommendations prior to raising the temperature.
  • Medical devices and portable humidifiers should be operated, cleaned, and disinfected per manufacturer instructions. Do not use tap water if sterile water is recommended.
  •  Drain garden hoses and shut off the water line when not in use for the season.
  •  Maintain chemical levels in your hot tub per manufacturer recommendations.
  •  Avoid high-risk activities. If you are at an increased risk for Legionnaires’ disease, consider avoiding power washing, or similar activities, which may generate increased amounts of aerosols or mist.


  • Complete this quick yes/no worksheet to determine if your building, or certain devices in your building, need a Water Management Program. Resources to help you develop a Water Management Program and for Legionella control in common sources of exposure are available at NJ Department of Health’s Legionella webpage. https://www.nj.gov/health/cd/topics/legion.shtml
  •  Store hot water at temperatures above 140°F and ensure hot water in circulation does not fall below 120°F (or at highest temperature allowable by local regulations and codes). Install thermostatic mixing valves as close as possible to fixtures to prevent scalding while permitting circulation hot water temperatures above 120°F.
  • Clean and maintain water system components, such as thermostatic mixing valves, aerators, showerheads, hoses, filters, storage tanks, and expansion tanks, regularly per manufacturer instructions.
  • Flush hot and cold water at all points of use (faucets, showers, drinking fountains) at least weekly to replace the water that has been standing in the pipes. Healthcare settings and facilities that house vulnerable populations should flush at least twice a week.
  • Remove dead legs or, where unavoidable, make them as short as possible (a section of pipe capped off with little or no water flow)Where a dead leg cannot be avoided, it should be flushed regularly to avoid water stagnation. This may require the installation of a drain valve.
  • Monitor water quality parameters such as temperature, disinfectant residuals, and pH regularly. Adjust frequency of monitoring based on stability of values. For example, increase frequency of monitoring if there is a high degree of measurement variability.
  • Safely operate and conduct regular maintenance of cooling towers to protect staff, visitors, and the adjacent community from exposure to Legionella. Use a Water Management Program to establish, track, and improve operation and maintenance activities. Resources to help you develop a Water Management Program for your cooling tower are available at the bottom of this section.

Follow recommendations from the NJ Department of Health when reopening your facility following a prolonged shutdown or reduced operation due to the COVID-19 Pandemic. Recommendations are available at: bit.ly/2XxlBaw


NJDOH receives approximately 250–350 reports of Legionnaires’ disease each year reported throughout New Jersey. Legionnaires’ disease is a type of pneumonia (lung infection) caused by the bacteria Legionella. Legionella is a type of bacteria found naturally in freshwater environments such as lakes and streams and becomes a health concern when it enters and grows inside human-made water systems. People can get Legionnaires’ disease by breathing in aerosolized (small droplets) water containing Legionella. Aerosolized water can come from plumbing systems and devices such as cooling towers (air-conditioning units for large buildings), hot tubs, cooling misters, and decorative fountains. Less commonly, people can get sick by aspiration of tap water containing Legionella. This happens when water accidently goes into the lungs while drinking (“goes down the wrong pipe”). People at increased risk of aspiration include those with swallowing difficulties. Home A/C units do not use water to cool, so these home units do not aerosolize water and are not a risk for Legionella growth. Legionnaires’ disease is generally not spread person to person.