Well water in Coos County, New Hampshire
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Testing recommended
private wells tested between 2006 and 2020 in Coos County had lead above the New Hampshire guidance level (15 ug/L), according to NH DHHS.
623 private wells tested 2006 to 2020 in state summaries; 1,224 test results across 17 contaminants from at least 161 wells, 1966 to 2022; nitrate has the most at 210. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
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.
An estimated 8,145 people in Coos County get their drinking water from a private well, per NH DHHS WISDOM, BRFSS 2020. That is about 37% of residents (survey range 29% to 46%).
Separately, the USGS national arsenic model estimates that 8% of the 9,807 people on private wells in Coos County draw water above 10 ug/L (the model's range is 6% to 11%), from geology and well depth rather than local tests.
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 | Above state level | Wells tested | Median | 95th pct | Highest | State level |
|---|---|---|---|---|---|---|
| Sodium | 427 | 348 | 20 mg/L | |||
| Iron | 431 | 22,300 | 300 ug/L | |||
| Lead (stagnant) | 346 | 721 | 15 ug/L | |||
| Copper (stagnant) | 346 | 10.1 | 1.3 mg/L | |||
| Manganese | 429 | 12,400 | 300 ug/L | |||
| Uranium | 430 | 270 | 30 ug/L | |||
| Arsenic | 436 | 29.4 | 5 ug/L | |||
| Chloride | 623 | 670 | 250 mg/L | |||
| Fluoride | 490 | 4.2 | 4 mg/L | |||
| Nitrate | 603 | 18 | 10 mg/L | |||
| Nitrite | 603 | 0.4 | 1 mg/L |
What individual samples found
Each row summarizes every public sample for that contaminant inside Coos 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 | Above limit | Samples | Detected | Median | Highest | Limit |
|---|---|---|---|---|---|---|
| Radium (226 + 228) 1988 to 2019 | 12 | 67% | 0 | 51.9 | 5 pCi/L EPA limit | |
| Fluoride 1966 to 2019 | 173 | 76% | 0.2 | 6.9 | 4 mg/L EPA limit | |
| Nitrate 1966 to 2019 | 210 | 54% | 0.063 | 11.8 | 10 mg/L EPA limit | |
| Arsenic 1986 to 2019 | 43 | 21% | 0 | 6 | 10 ug/L EPA limit | |
| Lead 1988 to 2019 | 37 | 16% | 0 | 10 | 15 ug/L EPA limit | |
| Copper 1988 to 2019 | 36 | 19% | 0 | 0.69 | 1.3 mg/L EPA limit | |
| Chloride 1966 to 2019 | no limit | 175 | 66% | 3.2 | 547 | 250 mg/L nuisance level |
| Manganese 1966 to 2019 | no limit | 170 | 62% | 22.5 | 4,400 | 300 ug/L health guideline |
| Iron 1966 to 2019 | no limit | 170 | 78% | 100 | 12,000 | 300 ug/L nuisance level |
| Sodium 1966 to 2019 | no limit | 159 | 89% | 5.8 | 300 | 20 mg/L health guideline |
| Radon 1986 to 2002 | no limit | 15 | 93% | 2,270 | 78,000 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: E. coli (4), Uranium (6), PFOA (4), PFOS (4), PFNA (3), PFHxS (3).
Closer than the county
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
Among homeowners in Coos County who sent a sample to the state lab, the health-based limits most often exceeded were lead (17% of 346 wells), copper (15% of 346 wells), and uranium (3% of 430 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.
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 Coos County
- 1Lead17% of 346 local wells tested were above the New Hampshire guidance level.
- 2Copper15% of 346 local wells tested were above the New Hampshire guidance level.
- 3Radium (226 + 228)8% of 12 local samples were above the limit.
- 4Uranium3% of 430 local wells tested were above the New Hampshire guidance level.
- 5Arsenic2% of 436 local wells tested were above the New Hampshire guidance level.
- 6Fluoride1% of 173 local samples were above the limit.
- 7Nitrate<1% of 210 local samples were above the limit.
- 8RadonMedian local reading is 2,270 pCi/L.
- 9Volatile organic compounds (VOCs)92 leaking underground storage tank sites on record locally.
- 10PFAS26 unlined landfills on record locally.
- 11Metals panel11 hazardous waste sites on record locally.
Test your Coos County well for lead, copper and radium (226 + 228)
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
Where to get a well tested in New Hampshire: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Coos County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Coos County
3,483 domestic wells in Coos County are on record with the state since 1984. 97% are drilled into bedrock, and the typical well is 305 feet deep (one in ten goes past 540 feet).
In a typical Coos County well, bedrock starts about 25 feet down, the median yield is 8 gallons per minute, 21% 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.
The rock under Coos County
Not a principal aquifer
The USGS map places this area outside any principal aquifer, which usually means wells here draw from fractured bedrock or thin local deposits rather than a large regional aquifer. Bedrock wells of that kind are where arsenic, radon and uranium turn up, and yields vary from well to well.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county centroid. A single well can sit in a different unit, especially near a boundary.
Official help in New Hampshire
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
Contamination sources on record in Coos County
NHDES records 92 leaking underground storage tank sites, 26 unlined landfills, 11 hazardous waste sites, and 38 reported spills and releases in Coos County, among 867 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.
- 92
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 26
- unlined landfillsOlder unlined landfills are a leading source of PFAS, VOCs and metals in nearby wells.
- 11
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 38
- reported spills and releasesMost spills are fuel; a few are solvents or chemicals that reach the water table.
- 274
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 18
- locally identified potential contamination sourcesTowns inventory these (vehicle repair, labs, salt piles, farms) when they draw wellhead protection maps.
- 1
- lined landfill or transfer facility
- 378
- other remediation projects
- 29
- other solid waste facilities
Treatment that fits the local profile
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
Sodium
Point-of-use reverse osmosis; Distillation
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
Radium (226 + 228)
Water softener (cation exchange); Point-of-use reverse osmosis
Systems we would look at first
Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For lead
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For lead
Acid neutralizing filter
whole-house, at the point of entry, about $1,200
Raises pH so plumbing stops leaching lead and copper.
For lead
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
For iron
Iron and manganese oxidizing filter
whole-house, at the point of entry, about $1,800
Air-injection or greensand media; fixes staining at the source.
Free, no obligation
Get on the list for a free in-home water test in Coos County
No water treatment company serves Coos County through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for Coos County, and you get an email naming it first.
Common questions
How deep are wells in Coos County?
The typical domestic well in Coos County is 305 feet deep, based on 3,483 wells reported to the state since 1984. One in ten is deeper than 540 feet. 97% are drilled into bedrock.
Is there arsenic in well water in Coos County?
Arsenic was detected in 21% of 43 public well samples in Coos County, and 0% 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 Coos County?
The median radon level across 15 public samples in Coos County was 2,270 pCi/L, with a high of 78,000 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Coos 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 Coos County
- Atkinson and Gilmanton Academy grantUSGS estimate
- Beans grantUSGS estimate
- Beans purchaseUSGS estimate
- BerlinUSGS estimate
- Cambridge townshipUSGS estimate
- CarrollUSGS estimate
- Chandlers purchaseUSGS estimate
- ClarksvilleUSGS estimate
- Colebrook20% lead
- Columbia0% nitrate
- Crawfords purchaseUSGS estimate
- Cutts grantUSGS estimate
- Dalton0% nitrate
- Dixs grantUSGS estimate
- Dixville townshipUSGS estimate
- DummerUSGS estimate
- ErrolUSGS estimate
- Ervings locationUSGS estimate
- GorhamUSGS estimate
- Greens grantUSGS estimate
- Hadleys purchaseUSGS estimate
- Jefferson12% lead
- Kilkenny townshipUSGS estimate
- Lancaster14% lead
- Low and Burbanks grantUSGS estimate
- Martins locationUSGS estimate
- Milan26% copper
- Millsfield townshipUSGS estimate
- NorthumberlandUSGS estimate
- Odell townshipUSGS estimate
- Pinkhams grantUSGS estimate
- Pittsburg15% copper
- Randolph20% uranium
- Sargents purchaseUSGS estimate
- Second College grantUSGS estimate
- Shelburne0% nitrate
- StarkUSGS estimate
- StewartstownUSGS estimate
- Stratford3% nitrate
- Success townshipUSGS estimate
- Thompson and Meserves purchaseUSGS estimate
- Wentworth locationUSGS estimate
- Whitefield14% lead
Counties near Coos County
Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.
Want the numbers themselves? Download the New Hampshire dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 1,212 samples in Coos 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.
- NHDES PFAS sampling: 12 samples in Coos County. PFAS results for private wells from the New Hampshire Department of Environmental Services Environmental Monitoring Database. Retrieved September 3, 2026.
- NH DHHS WISDOM private well summaries: summaries for 11 contaminants in Coos County, up to 623 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.
- USGS national arsenic model (Ayotte 2017): estimated share of 9,807 people on private wells in Coos County above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
- NHDES Water Well Inventory: 3,892 well records in Coos County, 3,483 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: 867 regulated sites located in Coos 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.