Well water in Union County, New Jersey
In Union County, 18% of 84 private wells tested between 2002 and 2024 had total coliform above the New Jersey limit (any detection), according to NJDEP.
84 private wells tested 2002 to 2024 in state summaries; 37 individual samples from 12 wells, 1968 to 2025. Data refreshed September 9, 2026.
What homeowner tests found
NJDEP Private Well Testing Act summaries: private wells tested and reported to the state, 2002 to 2024. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA.
| Contaminant | Wells tested | Above state level | Median | 95th pct | Highest | State level | |
|---|---|---|---|---|---|---|---|
| Total coliform | 84 | 18% | |||||
| Iron | 84 | 16% | 300 ug/L | ||||
| Manganese | 84 | 10% | 50 ug/L | ||||
| Gross alpha | 20 | 5% | 15 pCi/L | ||||
| E. coli Fecal coliform or | 84 | 4% | |||||
| Nitrate | 84 | 1% | 10 mg/L | ||||
| Arsenic | 84 | 0% | 5 ug/L | ||||
| Uranium | 17 | 0% | 30 ug/L |
What individual samples found
Each row summarizes every public sample for that contaminant inside Union County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Samples | Detected | Above limit | Median | Highest | Limit | |
|---|---|---|---|---|---|---|---|
| Arsenic 1985 to 2025 | 37 | 89% | 3% | 0.68 | 25.2 | 10 ug/L EPA limit |
Sampled fewer than 10 times, too few to summarize: PFOA (8), PFOS (8), Uranium (5), Radium (226 + 228) (4), Fluoride (3), Lead (1), Nitrate (1), Chloride (3).
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What this means
Among homeowners in Union County who sent a sample to the state lab, the health-based limits most often exceeded were total coliform (18% of 84 wells), E. coli (4% of 84 wells), and nitrate (1% of 84 wells). These are ordinary wells tested by their owners, so the shares are the best available picture of a typical well here, with one caveat: people test more often when they suspect a problem.
Iron exceeds the state's advisory level in a sizable share of wells; this is mostly a taste, staining or diet issue rather than a toxicity one.
What to test for in Union County
- Volatile organic compounds (VOCs)2 hazardous waste sites on record locally.
- Metals panel2 hazardous waste sites on record locally.
- Total coliform18% of 84 local wells tested were above the New Jersey limit (any detection).
- Iron16% of 84 local wells tested were above the New Jersey nuisance level.
- Manganese10% of 84 local wells tested were above the New Jersey nuisance level.
- Gross alpha5% of 20 local wells tested were above the New Jersey limit.
- E. coli4% of 84 local wells tested were above the New Jersey limit (any detection).
- Arsenic3% of 37 local samples were above the limit.
- Nitrate1% of 84 local wells tested were above the New Jersey limit.
- PFOAAbove the limit in 8 of 8 local samples; too few to quote a rate.
Contamination sources on record in Union County
NJDEP records 2 hazardous waste sites in Union County, among 3,689 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.
- 2
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 2,716
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 13
- lined landfills and transfer facilities
- 958
- other remediation projects
Treatment that fits the local profile
- Total coliform
- Inspect and repair the well cap and casing, then shock chlorinate and retest; UV disinfection whole-house; Chlorination system
- Gross alpha
- Point-of-use reverse osmosis; Water softener (cation exchange) for radium; Anion exchange for uranium
- Iron
- Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
- Manganese
- Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Chloride
- Point-of-use reverse osmosis; Distillation
Get your Union County water tested at home
A licensed local water treatment company tests your tap water in your home, walks you through the numbers, and quotes treatment only if something needs fixing. Free, about 30 minutes, no obligation. Tell us what you need and we match you with a company that serves Union County.
Common questions
Is there arsenic in well water in Union County?
Arsenic was detected in 89% of 37 public well samples in Union County, and 3% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How often should I test a private well in Union County?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Towns in Union County
- Berkeley Heights township10% total coliform
20 towns have fewer than 30 public samples and are included in the Union County totals above rather than shown separately: Clark township, Cranford township, Elizabeth, Fanwood borough, Garwood borough, Hillside township, Kenilworth borough, Linden, Mountainside borough, New Providence borough, Plainfield, Rahway, Roselle borough, Roselle Park borough, Scotch Plains township, Springfield township, Summit, Union township, Westfield, Winfield township.
Sources
- USGS Water Quality Portal: 70 samples in Union County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- NJDEP Private Well Testing Act summaries: summaries for 8 contaminants in Union County, up to 84 wells each. Share of private wells exceeding each standard in tests required at sale or lease under the New Jersey Private Well Testing Act, September 2002 to December 2024, published by NJDEP. Tests are untreated water at the time of sale or lease, so every well is counted once per transaction. Municipalities with fewer than ten wells are suppressed. Standards are New Jersey's: arsenic 5 ug/L, PFOA 14 ng/L, PFOS 13 ng/L, PFNA 13 ng/L, manganese and iron secondary standards. Uranium and PFAS were added to the required panel in 2021 and 2020, so their well counts are smaller. Retrieved September 9, 2026.
- NJDEP regulated sites: 3,689 regulated sites located in Union County. Known Contaminated Sites, regulated underground storage tank facilities and solid waste landfills from the New Jersey Department of Environmental Protection (NJ-GeoWeb). Retrieved September 9, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.