Private wells
New Jersey well water: who's on a well and what to test for
People on private wells
754,500
Homes on wells
7.9%
Est. above arsenic limit
40,600
Every New Jersey county
Sorted by people on private wells. Arsenic and nitrate are modeled for typical wells in the county, not measured at yours; depth is the median of domestic well records.
| Morris County | 87,500 | 16% | 2.6% | 1.6 | 150 ft |
| Hunterdon County | 76,400 | 58% | 6.9% | 2.0 | 200 ft |
| Sussex County | 72,200 | 50% | 2.1% | 0.8 | 200 ft |
| Burlington County | 62,900 | 12% | 2.4% | 0.5 | 120 ft |
| Cumberland County | 58,700 | 44% | 1.9% | 3.1 | 98 ft |
| Bergen County | 54,100 | 6% | 2.5% | 2.6 | 150 ft |
| Atlantic County | 42,600 | 13% | 2.8% | 0.9 | 100 ft |
| Warren County | 40,800 | 36% | 2.1% | 1.4 | 172 ft |
| Ocean County | 37,900 | 5% | 2.7% | 1.0 | 85 ft |
| Monmouth County | 37,500 | 5% | 1.7% | 0.8 | 145 ft |
| Gloucester County | 37,100 | 12% | 2.2% | 2.7 | 100 ft |
| Cape May County | 36,800 | 19% | 2.9% | 0.5 | 90 ft |
| Salem County | 26,200 | 38% | 2.2% | 1.7 | 100 ft |
| Passaic County | 23,800 | 5% | 1.8% | 1.2 | 170 ft |
| Middlesex County | 20,000 | 2% | 3.3% | 2.1 | 110 ft |
| Mercer County | 17,400 | 4% | 4.4% | 2.5 | 130 ft |
| Somerset County | 13,600 | 4% | 8.2% | 2.1 | 150 ft |
| Camden County | 7,600 | 1% | 2.6% | 1.7 | 100 ft |
| Essex County | 1,200 | 0% | 2.8% | 1.6 | 125 ft |
| Union County | 250 | 0% | 1.8% | 1.6 | 125 ft |
| Hudson County | 0 | 0% | 2.9% | 1.9 | 200 ft |
Shading: red is among the highest counties nationally, amber the middle, green the lower range. Click a column to sort.
Most well users above the arsenic limit
- Gloucester County: about 5,300 people
- Burlington County: about 4,900 people
- Atlantic County: about 4,800 people
- Cumberland County: about 4,400 people
- Ocean County: about 4,000 people
Highest modeled nitrate
- Cumberland County: 3.1 mg/L average (limit 10)
Test first, then treat what the test finds
We may earn a commission from links below, at no cost to you. Picks follow the testing order, not who pays. How we make money.
1. Certified lab well test
Start here, every year
A mail-in kit analyzed by a certified lab measures bacteria, nitrate, arsenic, metals and more. Test strips cannot measure arsenic or uranium reliably.
2. Sediment pre-filter
Sand, silt or cloudy water
A 5-micron cartridge after the pressure tank catches sand, silt and rust before they reach fixtures or other filters. Cartridges are cheap and swap every few months.
3. Iron and sulfur filter
Orange stains or rotten-egg smell
Air-injection or oxidizing-media filters remove orange staining and rotten-egg smell. Size one from a lab result for iron, manganese and hydrogen sulfide.
4. UV disinfection system
Coliform bacteria in a test
Inactivates bacteria and viruses; usually for private wells or after boil notices.
5. Under-sink reverse osmosis
Arsenic, nitrate or uranium in a test
The most thorough option for drinking water: PFAS, lead, nitrate, arsenic and more. Look for NSF/ANSI 58.
6. Whole-house well filter
Several problems at once
Multi-stage sediment and carbon for every tap. Add UV if bacteria shows up, and choose stages from your lab results, not a guess.
Questions
Which New Jersey counties rely most on wells?+
By share of homes: Hunterdon County (58%), Sussex County (50%), Cumberland County (44%), Salem County (38%), Warren County (36%). By number of people: Morris County (87,500), Hunterdon County (76,400), Sussex County (72,200).
Is arsenic a problem in New Jersey wells?+
USGS estimates about 40,600 New Jersey well users have water above the 10 microgram per liter arsenic limit that applies to public systems, the largest numbers in Gloucester County, Burlington County, Atlantic County. Arsenic has no taste or smell, so only a lab test finds it.
Do I have to test my well when I sell a house in New Jersey?+
Yes. The seller (or the buyer, by contract) must test the well before closing for bacteria, nitrate, arsenic, lead, gross alpha, PFAS and other parameters (Private Well Testing Act).
How often should I test my well?+
No federal law covers private wells. EPA's drinking water limits apply to public water systems, so testing and treating a private well is up to the owner. EPA and CDC recommend testing at least once a year for coliform bacteria, nitrate, pH and total dissolved solids, and testing for arsenic, uranium, radon and other local concerns based on where you live.
Well-user counts, arsenic and nitrate figures are each a modeled estimate built from national datasets, not a count of tested wells, and well depths summarize drilling records rather than every well. Your own well can be very different from the county average, which is why the only answer for your home is a lab test. Sources: EPA Office of Research and Development, Water Source 2020 (private well estimates by census block); CDC Environmental Public Health Tracking, Well Water Index (from USGS nitrate and arsenic models); USGS, county-level domestic well population with arsenic above 10 micrograms per liter (Ayotte and others, 2017); USGS Synthesized Domestic Well Database for the Conterminous United States (SynDWell-US), McCarthy and others, 2025 (depth, where a county has 30+ usable records).