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Posted on: April 20, 2023

TWW's Low-Velocity Water Main Flushing Program Begins Next Week

Trenton, N.J. — Trenton Water Works (TWW) announced today that it would begin low-velocity flushing of water mains using specialized equipment throughout its 683-mile water distribution system next week. This activity will continue through May. TWW personnel will execute the flushing during regular business hours, Monday to Friday, 8:30 a.m. to 4:30 p.m. Equipment used by TWW personnel may sometimes remain in place overnight with signage.


"The goal of the low-velocity water main flushing is to mitigate conditions that promote the growth of pathogens, including Legionella, by increasing and sustaining chlorine residuals," said Sean Semple, Acting Director of the city's Department of Water and Sewer, which operates Trenton Water Works, one of the oldest public water systems in the United States. "Once we achieve this water-treatment goal, we will execute additional action steps to improve water quality in the TWW system."  


Low-velocity water main flushing is a conventional water-industry method that uses specialized equipment attached to a fire hydrant to restrict the flow to such levels that the sediment within a water main is not disturbed or scoured. The procedure also allows for eliminating stagnant water and optimizing chlorine disinfection to minimize the conditions contributing to pathogens' growth, such as Legionella, a type of bacterium found naturally in freshwater environments (e.g., lakes and streams).


During the flushing program, service-area residents should not notice any changes in their water, such as brown or discolored water. However, residents may notice a chlorine smell as TWW personnel work to increase chlorine levels in parts of the water distribution system.


TWW is working with the New Jersey Department of Environmental Protection (NJDEP) and the New Jersey Department of Health (NJDOH) on Legionella mitigation. TWW provides weekly updates on this work every Friday on its Legionella Mitigation, Updates, and Information webpage at


TWW has expanded systemwide monitoring for Legionella via sampling locations approved by the NJDEP, including storage tanks, the water-filtration plant on Route 29 South in Trenton, and the 100 million-gallon Pennington Avenue Reservoir.


On April 3, several teams comprising personnel from the Environmental Protection Agency (EPA), the NJDEP, and TWW commenced taking and analyzing water samples from fire hydrants in TWW's service area to determine which parts of its water distribution system will undergo low-velocity water main flushing, data that will inform flushing activity throughout the system in the weeks and months ahead.


TWW customers and service-area residents can learn more about Legionella at the NJDEP's webpage at


If you have questions about TWW's Legionella mitigation, call its Office of Communications and Community Relations at (609) 989-3033, Monday to Friday, 8:30 a.m. to 4:30 p.m.


Purchased by the City of Trenton in 1859, Trenton Water Works (TWW) is one of the oldest and largest publicly owned water systems in the United States. TWW supplies approximately 28 million gallons of water per day to a quarter-million consumers in a five-municipality service area comprised of Trenton, Ewing Township, parts of Hamilton Township, Lawrence Township, and Hopewell Township. TWW operates a 60-million-gallon water-filtration plant and water-distribution system that consists of a 100-million-gallon reservoir, 683 miles of water mains, three pump stations, nearly 8,000 valves, 3,517 fire hydrants, and six interconnections between TWW and other water suppliers. TWW serves approximately 63,000 metered customers.


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