Well water in Hillsborough County, New Hampshire
In Hillsborough County, 24% of 3,558 private wells tested between 2006 and 2020 had arsenic above the New Hampshire guidance level (5 ug/L), according to NH DHHS.
4,530 private wells tested 2006 to 2020 in state summaries; 3,795 individual samples from 1,768 wells, 1963 to 2026. Data refreshed September 3, 2026.
NHDES samples private wells near known or suspected PFAS sources (industrial sites, airports, landfills, fire training areas), and wells with a detection are resampled over time. PFAS shares describe wells that were tested for a reason, not every well in the area. In that targeted sampling, 61% of 3,781 PFOA results in Hillsborough County were above the EPA limit of 4 ng/L. In that targeted sampling, 10% of 3,795 PFOS results in Hillsborough County were above the EPA limit of 4 ng/L.
An estimated 63,812 people in Hillsborough County get their drinking water from a private well, per NH DHHS WISDOM, BRFSS 2020.
What homeowner tests found
NH DHHS WISDOM private well summaries: private wells tested and reported to the state, 2006 to 2020. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA. County and state figures combine the town summaries, weighted by wells tested; medians are not combined.
| Contaminant | Wells tested | Above state level | Median | 95th pct | Highest | State level | |
|---|---|---|---|---|---|---|---|
| Radon | 695 | 47% | 380,000 | 2,000 pCi/L | |||
| Sodium | 3,286 | 43% | 633 | 20 mg/L | |||
| Arsenic | 3,558 | 24% | 523 | 5 ug/L | |||
| Iron | 3,290 | 15% | 87,800 | 300 ug/L | |||
| Lead (stagnant) | 1,580 | 15% | 31,200 | 15 ug/L | |||
| Copper (stagnant) | 1,576 | 14% | 315 | 1.3 mg/L | |||
| Manganese | 3,290 | 7% | 4,200 | 300 ug/L | |||
| Uranium | 3,323 | 5% | 584 | 30 ug/L | |||
| Chloride | 3,631 | 3% | 1,300 | 250 mg/L | |||
| Nitrate | 2,119 | <1% | 34 | 10 mg/L | |||
| Fluoride | 4,530 | <1% | 9.1 | 4 mg/L | |||
| Nitrite | 2,118 | 0% | 0.8 | 1 mg/L |
What individual samples found
Each row summarizes every public sample for that contaminant inside Hillsborough 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 | |
|---|---|---|---|---|---|---|---|
| PFOA 2019 to 2026 | 3,781 | 96% | 61% | 5.8 | 200 | 4 ng/L EPA limit | |
| Arsenic 1986 to 2022 | 225 | 58% | 20% | 1 | 140 | 10 ug/L EPA limit | |
| PFOS 2019 to 2026 | 3,795 | 74% | 10% | 0.97 | 71 | 4 ng/L EPA limit | |
| Uranium 1999 to 2022 | 185 | 54% | 5% | 0.096 | 390 | 30 ug/L EPA limit | |
| Copper 1986 to 2022 | 85 | 71% | 4% | 0.005 | 6.82 | 1.3 mg/L EPA limit | |
| PFHxS 2020 to 2026 | 3,793 | 82% | <1% | 0.79 | 170 | 10 ng/L EPA limit | |
| Fluoride 1963 to 2021 | 177 | 79% | <1% | 0.2 | 4.5 | 4 mg/L EPA limit | |
| Nitrate 1963 to 2021 | 336 | 69% | <1% | 0.1 | 16 | 10 mg/L EPA limit | |
| PFNA 2020 to 2026 | 3,644 | 22% | <1% | 0 | 25 | 10 ng/L EPA limit | |
| Lead 1986 to 2022 | 208 | 61% | 0% | 0 | 8.73 | 15 ug/L EPA limit | |
| Radium (226 + 228) 1986 to 2019 | 16 | 94% | 0% | 0 | 1.8 | 5 pCi/L EPA limit | |
| Manganese 1963 to 2022 | 432 | 81% | no limit | 0 | 2,880 | 300 ug/L health guideline | |
| Sodium 1963 to 2021 | 260 | 96% | no limit | 12.3 | 540 | 20 mg/L health guideline | |
| Chloride 1963 to 2021 | 229 | 85% | no limit | 11 | 509 | 250 mg/L nuisance level | |
| Radon 1986 to 2003 | 36 | 100% | no limit | 1,350 | 64,000 | 2,000 pCi/L health guideline | |
| Iron 1963 to 2013 | 15 | 67% | no limit | 180 | 2,800 | 300 ug/L nuisance level |
Sampled fewer than 10 times, too few to summarize: E. coli (2).
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What this means
Among homeowners in Hillsborough County who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (24% of 3,558 wells), lead (15% of 1,580 wells), and copper (14% of 1,576 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.
Radon was above the New Hampshire guidance level of 2,000 pCi/L in 47% of 695 wells. Radon in water matters because it moves into indoor air during showers and laundry.
Sodium and iron exceed the state's advisory level in a sizable share of wells; these are mostly a taste, staining or diet issue rather than a toxicity one.
What to test for in Hillsborough County
- Volatile organic compounds (VOCs)379 leaking underground storage tank sites on record locally.
- PFAS60 unlined landfills on record locally.
- Metals panel206 hazardous waste sites on record locally.
- PFOA61% of 3,781 local samples were above the limit.
- Radon47% of 695 local wells tested were above the New Hampshire guidance level.
- Sodium43% of 3,286 local wells tested were above the New Hampshire guidance level.
- Iron15% of 3,290 local wells tested were above the New Hampshire guidance level.
- Lead15% of 1,580 local wells tested were above the New Hampshire guidance level.
- PFOS10% of 3,795 local samples were above the limit.
- Manganese7% of 3,290 local wells tested were above the New Hampshire guidance level.
- Chloride3% of 3,631 local wells tested were above the New Hampshire guidance level.
Wells in Hillsborough County
19,719 domestic wells in Hillsborough County are on record with the state since 1984. 98% are drilled into bedrock, and the typical well is 400 feet deep (one in ten goes past 700 feet).
In a typical Hillsborough County well, bedrock starts about 17 feet down, the median yield is 7 gallons per minute, 20% of wells yield under 3 gallons per minute and usually need a storage tank.
Bedrock wells are where arsenic, uranium and radon come from: the water sits in fractures in granite and metamorphic rock and picks up whatever the rock carries. That is why testing for those three matters more here than in a dug or gravel well.
Find your own well's report
The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.
- Open NHDES OneStop and choose Water Well.
- Enter your town and one word of your street name. Leave out the house number and the Road or Street part; a short search matches more.
- In the results, click Show for your address to see the report: total depth, depth to bedrock, casing, yield in gallons per minute, static water level, and the driller.
- Save Results exports the whole list to a spreadsheet.
Reports exist only for wells drilled since January 1984, when reporting became mandatory, and street names are as they were when the well was drilled.
Contamination sources on record in Hillsborough County
NHDES records 379 leaking underground storage tank sites, 60 unlined landfills, 206 hazardous waste sites, and 246 reported spills and releases in Hillsborough County, among 4,162 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.
- 379
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 60
- unlined landfillsOlder unlined landfills are a leading source of PFAS, VOCs and metals in nearby wells.
- 206
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 246
- reported spills and releasesMost spills are fuel; a few are solvents or chemicals that reach the water table.
- 971
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 369
- locally identified potential contamination sourcesTowns inventory these (vehicle repair, labs, salt piles, farms) when they draw wellhead protection maps.
- 2
- lined landfills and transfer facilities
- 1,868
- other remediation projects
- 61
- other solid waste facilities
Treatment that fits the local profile
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Lead
- Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching
- Copper
- Neutralizing filter to raise pH; Point-of-use reverse osmosis
- Radon
- Aeration (bubble-up or diffused) whole-house; Granular activated carbon whole-house (lower levels only)
- Sodium
- Point-of-use reverse osmosis; Distillation
- PFOA
- Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
Book a free water test in Hillsborough County
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.
Common questions
How deep are wells in Hillsborough County?
The typical domestic well in Hillsborough County is 400 feet deep, based on 19,719 wells reported to the state since 1984. One in ten is deeper than 700 feet. 98% are drilled into bedrock.
Is there arsenic in well water in Hillsborough County?
Arsenic was detected in 58% of 225 public well samples in Hillsborough County, and 20% 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 high is radon in well water in Hillsborough County?
The median radon level across 36 public samples in Hillsborough County was 1,350 pCi/L, with a high of 64,000 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Hillsborough 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 Hillsborough County
- Amherst20% copper
- Antrim37% arsenic
- Bedford17% lead
- Brookline8% uranium
- Deering29% arsenic
- Francestown48% arsenic
- Goffstown62% arsenic
- Greenfield41% arsenic
- Hancock56% arsenic
- Hillsborough32% arsenic
- Hollis38% arsenic
- Hudson53% arsenic
- Litchfield473 samples
- Merrimack3% arsenic
- Milford21% uranium
- Mont Vernon18% uranium
- Nashua39 samples
- New Boston41% arsenic
- New Ipswich34% arsenic
- Pelham48% arsenic
- Peterborough41% arsenic
- Temple39% arsenic
- Weare39% arsenic
- Wilton9% arsenic
7 towns have fewer than 30 public samples and are included in the Hillsborough County totals above rather than shown separately: Bennington, Greenville, Lyndeborough, Manchester, Mason, Sharon, Windsor.
Sources
- NHDES PFAS sampling: 15,009 samples in Hillsborough County. PFAS results for private wells from the New Hampshire Department of Environmental Services Environmental Monitoring Database. Retrieved September 3, 2026.
- USGS Water Quality Portal: 2,210 samples in Hillsborough 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.
- NH DHHS WISDOM private well summaries: summaries for 12 contaminants in Hillsborough County, up to 4,530 wells each. Town summaries of private well tests run by the New Hampshire Public Health Laboratories, published by NH DHHS through the WISDOM environmental public health tracking portal. Exceedance shares use New Hampshire guidance levels, which are stricter than EPA for arsenic (5 ug/L), manganese (0.3 mg/L), radon (2,000 pCi/L) and sodium (20 mg/L). Statistics for small counts are suppressed (*). Retrieved September 3, 2026.
- NHDES Water Well Inventory: 22,224 well records in Hillsborough County, 19,719 domestic. Well construction records reported to the New Hampshire Department of Environmental Services Water Well Board. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 3, 2026.
- NHDES OneStop regulated sites: 4,162 regulated sites located in Hillsborough County. Remediation sites, underground storage tanks, solid waste facilities and potential contamination sources from the New Hampshire Department of Environmental Services OneStop database. Retrieved September 3, 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.