New Jersey Private Well Water Risk: Arsenic & Nitrate
These figures are USGS statistical estimates for private (domestic) wells in New Jersey. They describe the area's modeled risk — not any single well.
Quick answer: Yes — arsenic occurs naturally in New Jersey groundwater. USGS modeling estimates about 40,563 New Jersey residents rely on private wells with arsenic above the EPA limit of 10 µg/L. The highest modeled exposure is in Gloucester County (~5,321), Burlington County (~4,874), Atlantic County (~4,783). For nitrate, about 1.1% of New Jersey's ~766,000 private-well residents are modeled above the 10 mg/L limit. These are area estimates, not a test of your well — arsenic has no taste or smell, so only a certified lab test tells you your level.
This is a modeled probability for the area, not a measurement of your well. USGS statistical models estimate how many private wells in this area are likely to exceed the federal limit — they cannot tell you what is in your water. Two neighbors can have very different results. The only way to know your well is to test it.
Nitrate
1.1%
of the private-well population is modeled above the 10 mg/L nitrate limit
~8,500
people on wells estimated above the limit
~766,000
total residents on private wells statewide
Source: USGS machine-learning nitrate model, Ransom et al. (2022), domestic-well depth zone.
Find out what's actually in your well
New Jersey has one of the higher modeled arsenic exposures in the country — but that number is an area estimate, not your well. Arsenic, nitrate and coliform bacteria are the three most common private-well problems, and none of them has a taste or smell. A certified lab test checks all of them at once; the CDC and EPA recommend testing every well at least once a year.
Basic screening only. Confirm arsenic, nitrate and bacteria with a certified lab.
Find a certified drinking-water labAmazon links are affiliate links — we may earn a commission at no extra cost to you.
Arsenic
Across New Jersey, an estimated ~40,563 people rely on private wells with modeled arsenic above the 10 µg/L EPA limit. The highest modeled exposure is in Gloucester County (~5,321 people).
Counties with the highest modeled arsenic exposure
| County | Est. well residents over arsenic limit | 90% range |
|---|---|---|
| Gloucester County | ~5,321 | 3,498–7,840 |
| Burlington County | ~4,874 | 3,195–7,254 |
| Atlantic County | ~4,783 | 3,138–7,207 |
| Cumberland County | ~4,410 | 2,956–6,568 |
| Ocean County | ~3,975 | 2,586–6,008 |
| Camden County | ~3,421 | 2,248–4,963 |
| Cape May County | ~2,593 | 1,800–3,793 |
| Monmouth County | ~1,816 | 1,244–2,654 |
| Morris County | ~1,686 | 1,118–2,590 |
| Salem County | ~1,633 | 1,084–2,424 |
| Hunterdon County | ~1,426 | 951–2,165 |
| Sussex County | ~1,235 | 984–1,561 |
| Passaic County | ~1,144 | 572–2,219 |
| Somerset County | ~648 | 435–959 |
| Mercer County | ~595 | 407–904 |
| Bergen County | ~448 | 296–678 |
| Warren County | ~411 | 336–505 |
4 additional New Jersey counties have lower modeled arsenic exposure (fewer than 100 estimated well residents over the limit). Of these, 3 have measured USGS well samples: Essex, Middlesex, Union.
Source: USGS domestic-well arsenic model, Lombard et al. (2021); county population product (2017).
Measured well tests by county
The USGS has published laboratory results from wells in 20 New Jersey counties (at least 5 wells each). These are real measurements of other wells — domestic, public-supply and monitoring wells — not a test of yours. The tables rank counties by the share of sampled wells over each federal threshold.
Nitrate (as N): counties with the most wells > 10 mg/L (EPA MCL)
| County | Wells over | Median | Sampled |
|---|---|---|---|
| Salem County | 43% | 7.5 mg/L | 68 wells |
| Cumberland County | 25% | 5.1 mg/L | 103 wells |
| Monmouth County | 7% | 0 mg/L | 44 wells |
| Atlantic County | 6% | 1.1 mg/L | 80 wells |
| Mercer County | 5% | 1.9 mg/L | 81 wells |
| Middlesex County | 4% | 0.8 mg/L | 83 wells |
| Cape May County | 4% | 0.3 mg/L | 67 wells |
| Camden County | 3% | 1.2 mg/L | 91 wells |
| Somerset County | 3% | 1.9 mg/L | 32 wells |
| Gloucester County | 2% | 2.5 mg/L | 195 wells |
Manganese: counties with the most wells > 300 µg/L (EPA health advisory)
| County | Wells over | Median | Sampled |
|---|---|---|---|
| Morris County | 25% | 20 µg/L | 305 wells |
| Middlesex County | 23% | 62 µg/L | 82 wells |
| Union County | 17% | 2 µg/L | 6 wells |
| Essex County | 15% | 8 µg/L | 13 wells |
| Mercer County | 14% | 7 µg/L | 79 wells |
| Monmouth County | 14% | 74 µg/L | 51 wells |
| Passaic County | 13% | 9 µg/L | 32 wells |
| Burlington County | 9% | 34 µg/L | 99 wells |
| Bergen County | 9% | 2 µg/L | 55 wells |
| Cape May County | 7% | 34 µg/L | 135 wells |
Source: USGS ScienceBase 5f36baa782cee144fb3873e8 (manganese, pH, arsenic) and McMahon et al. (2019), Environ. Sci. Technol. 53:29–38 (nitrate, iron); aggregated by county with Census 2020 boundaries. USGS well samples; not a test of your well.
Acidic well water in New Jersey (low pH)
50% of 2,183 USGS-sampled wells in New Jersey had pH below 6.5. Acidic water corrodes copper pipes and fixtures and can leach lead and copper into your tap water — the usual fix is a whole-house acid neutralizer (calcite for mildly acidic water, soda-ash injection for very low pH). Counties with the highest share of acidic wells:
| County | Wells below pH 6.5 | Median pH | Sampled |
|---|---|---|---|
| Cumberland County | 89% | 4.8 | 116 wells |
| Gloucester County | 83% | 4.9 | 253 wells |
| Atlantic County | 79% | 4.9 | 104 wells |
| Burlington County | 76% | 5.0 | 105 wells |
| Camden County | 72% | 5.1 | 101 wells |
| Ocean County | 71% | 5.1 | 189 wells |
| Salem County | 68% | 5.3 | 104 wells |
| Monmouth County | 62% | 6.2 | 76 wells |
| Middlesex County | 57% | 6.1 | 110 wells |
| Cape May County | 39% | 7.2 | 143 wells |
Source: USGS ScienceBase 5f36baa782cee144fb3873e8 (pH). Measured other wells, not a test of yours.
Match the filter to your test result
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New Jersey well water: FAQ
Is there arsenic in well water in New Jersey?
Yes. USGS modeling estimates about 40,563 people in New Jersey use private wells with arsenic above 10 µg/L, across 21 modeled counties. Arsenic comes from natural bedrock and varies well to well, even between neighbors, so a lab test is the only way to know your own level.
Which New Jersey counties have the most arsenic in well water?
By modeled number of well residents over the arsenic limit: Gloucester County (~5,321), Burlington County (~4,874), Atlantic County (~4,783). Counties with more private-well users rank higher, so a smaller county can still have a high share of affected wells.
How do I remove arsenic from well water in New Jersey?
Test first. If arsenic is present, a point-of-use reverse-osmosis system under the kitchen sink removes 90%+ of it; boiling does not remove arsenic (it concentrates it), and carbon pitchers and water softeners do not remove it either. Whole-house adsorptive arsenic media is used when levels are high. Re-test after installing and then annually.
Is nitrate a problem in New Jersey well water?
USGS models about 1.1% of New Jersey's private-well population (~8,500 people) above the 10 mg/L nitrate limit. Nitrate is highest in shallow wells near fertilized cropland, septic systems or livestock, and matters most for infants and pregnancy.
Do I need an acid neutralizer for my well in New Jersey?
Acidic well water is common in New Jersey. In USGS lab results from 2,183 wells across 20 New Jersey counties, 50% had pH below 6.5. The most acidic sampled counties are Cumberland County (89% of 116 wells), Gloucester County (83% of 253 wells), Atlantic County (79% of 104 wells). You only need a neutralizer if your own well tests below about 6.5 — signs include blue-green stains on fixtures and pinhole leaks in copper pipe. A calcite (or calcite/Corosex) neutralizer tank handles mildly acidic water (roughly pH 6–6.5); very acidic water usually needs soda-ash injection. Test first-draw lead and copper too, since acidic water dissolves both from plumbing.
High manganese in New Jersey well water — what should I do?
In USGS lab results from 1,904 wells across 20 New Jersey counties, 9% were above the EPA's 300 µg/L health advisory for manganese and 29% were above the 50 µg/L level where it stains fixtures and laundry black or brown. Sampled counties with the highest share over the health advisory: Morris County (25% of 305 wells), Middlesex County (23% of 82 wells), Union County (17% of 6 wells). If your own test is over 300 µg/L, don't use the water for infant formula and use another source for drinking and cooking until it is treated — high manganese is linked to neurological effects, especially in babies and children. Boiling does not remove it. For the whole house, an oxidizing filter (greensand, Birm or air-injection) handles manganese, usually alongside iron; a water softener can remove low levels. For drinking water, a point-of-use reverse osmosis system reduces manganese at the kitchen tap. Retest after treatment to confirm it worked.