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Health Indicator Report of Fecal Coliform or E. coli in Private Wells

Coliform bacteria are organisms that are present in the environment and in the feces of all warm-blooded animals and humans. Coliform bacteria will not likely cause illness. However, their presence in drinking water indicates that disease-causing organisms (pathogens) could be in the water system. Most pathogens that contaminate water supplies come from the feces of humans or animals. Testing drinking water for all possible pathogens is complex, time-consuming, and expensive. It is relatively easy and inexpensive to test for coliform bacteria.

Fecal Coliform or E. Coli in Private Wells Percent of Wells with Fecal Coliform or E. Coli Detected, by County, September 2002 through December 2018


**Results by county are suppressed when the number of tested wells was less than 10. Denominator is the number of tested private wells. Data Source: NJ Department of Environmental Protection, Division of Water Supply and Geoscience, and Division of Science, Research, and Environmental Health, obtained on March 2, 2020.

Data Interpretation Issues

Under the PWTA, all wells are tested for the presence of a group of bacteria called total coliform (TC). When TC is detected, the sample is further tested for either fecal coliform or E. coli bacteria, depending on the testing laboratory. The presence of either fecal coliform or E. coli is strong evidence that a well has been contaminated with fecal waste, which can come from either human (septic tanks, leaking sewer lines) or animal (surface water infiltration) sources. Statewide, fecal coliform or E. coli were detected in 2.0 percent of all sampled wells. The counties in the Coastal Plain had the lowest percentage of wells in which either fecal coliform or E. coli was detected. It is believed that the sand and clay layers of the Coastal Plain better protect wells from fecal contamination than fractured rock formations in the northern part of the State.


Percent of tested private wells with fecal coliform or E. coli detected


Number of tested private wells with fecal coliform or E. coli detected


Number of tested private wells in a specified period of time

How Are We Doing?

Between September 2002 and December 2018, fecal coliform or E. coli was detected in 2.0 % of 111,010 private wells in sampled New Jersey. Fecal coliform or E. coli was most commonly detected in Somerset (4.3% of wells), Sussex (4.2% of wells), Passaic (3.4% of wells), Hunterdon (3.2% of wells), Warren (3.2% of wells), Mercer (2.9% of wells) and Union (2.8% of wells) Counties. Online maps showing detection of fecal coliform or E. coli are available at the county level, municipal level, and for 2 mile by 2 mile grids from NJDEP, [].

What Is Being Done?

The New Jersey Private Well Testing Act (N.J.S.A. 58:12A-26 et seq.) became effective in September 2002. The PWTA requires the buyer or the seller of a property to test untreated well water prior to the sale and review the results prior the closing of title. It also requires landlords to test the private well water supplied to their tenants every five years and provide their tenants with a written copy of the results. The data generated by this program are provided to the homeowners by the laboratory performing the analyses and then sent to the New Jersey Department of Environmental Protection (NJDEP). The NJDEP notifies local health agencies when a well within their jurisdiction is tested under the PWTA. The data from the PWTA are used by NJDEP to assess the quality of the water from private wells throughout the state.

Available Services

If your drinking water comes from a private well, you are responsible for testing. The NJDEP recommends that you use a laboratory that is NJDEP-certified. You can call the NJDEP Office of Quality Assurance at (609) 292-3950 for information on laboratories certified to test drinking water or look for the information online at: [] using the "Search by Category" option, select "Certified Laboratories", and search for "Certified Drinking Water Labs", "PWTA Laboratories Certified for Sampling", or "Laboratories Certified by Parameter". Testing is required for sale of residential real estate when a private well is the source of drinking water. For more information, contact the NJDEP Private Well Testing Program at (866) 479-8378 or visit: [] Private Well Testing Act Frequently Asked Questions: [] NJ Private Well Testing Act Data Summary, by county, municipality, and 2 mile by 2 mile grid: [] NJDOH Drinking Water Facts: Private Wells, [] NJDOH Drinking Water and Public Health Project, [] To inquire about New Jersey well permitting and regulation, contact the NJDEP Division of Water Supply at (609) 984-6831. For information on federal drinking water regulations, and other water safety issues, contact the United States Environmental Protection Agency Safe Drinking Water Hotline at (800) 426-4791.
Page Content Updated On 03/03/2020, Published on 03/03/2020
The information provided above is from the Department of Health's NJSHAD web site ( The information published on this website may be reproduced without permission. Please use the following citation: " Retrieved Sat, 02 March 2024 7:17:14 from Department of Health, New Jersey State Health Assessment Data Web site: ".

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