Well water in Henniker, New Hampshire

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Testing strongly recommended

private wells tested between 2006 and 2020 in Henniker had arsenic above the New Hampshire guidance level (5 ug/L), according to NH DHHS.

221 private wells tested 2006 to 2020 in state summaries; 100 test results across 10 contaminants from at least 14 wells, 1986 to 1989; nitrate has the most at 17. Data refreshed September 3, 2026.

Compiled by Nick at Well Water Nerd from public records. How these pages are built

Separately, a USGS and NHDES statistical model puts the chance that a bedrock well in Henniker exceeds 5 ug/L of arsenic at 28% (as low as 5% in parts of town), based on geology rather than 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.

Contaminant	Above state level	Wells tested	Median	95th pct	Highest	State level
Arsenic	33%	189	2.5	21	199	5 ug/L
Radon	31%	61	1,038	8,392	19,281	2,000 pCi/L
Sodium	19%	182	9.8	68.6	387	20 mg/L
Iron	16%	181	100	1,200	2,600	300 ug/L
Copper (stagnant)	10%	134	0.1	2.7	5.7	1.3 mg/L
Lead (stagnant)	10%	134	1.6	20.1	73.2	15 ug/L
Manganese	3%	182	0	200	800	300 ug/L
Chloride	2%	209	2.1	130	1,100	250 mg/L
Fluoride	<1%	221	0.3	2.3	5.9	4 mg/L
Uranium	<1%	181	0.7	3.2	37	30 ug/L
Nitrate	0%	209	0	0.9	9.1	10 mg/L
Nitrite	0%	208	0	0	0.1	1 mg/L

What individual samples found

Each row summarizes every public sample for that contaminant inside Henniker. 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
Fluoride 1986 to 1989	13%	15	93%	0.4	4.5	4 mg/L EPA limit
Nitrate 1986 to 1989	0%	17	12%	0	1.73	10 mg/L EPA limit
Chloride 1986 to 1989	no limit	16	44%	0	31	250 mg/L nuisance level
Manganese 1986 to 1989	no limit	15	53%	3	570	300 ug/L health guideline
Sodium 1986 to 1989	no limit	15	87%	10	29	20 mg/L health guideline
Iron 1986 to 1989	no limit	15	93%	400	6,400	300 ug/L nuisance level

Sampled fewer than 10 times, too few to summarize: Lead (1), Arsenic (2), Copper (1), Radon (3).

Closer than the town

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 address

What this means

Among homeowners in Henniker who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (33% of 189 wells), copper (10% of 134 wells), and lead (10% of 134 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 31% of 61 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 Henniker

1
Arsenic
33% of 189 local wells tested were above the New Hampshire guidance level.
2
Fluoride
13% of 15 local samples were above the limit.
3
Copper
10% of 134 local wells tested were above the New Hampshire guidance level.
4
Lead
10% of 134 local wells tested were above the New Hampshire guidance level.
5
Uranium
<1% of 181 local wells tested were above the New Hampshire guidance level.
6
Radon
31% of 61 local wells tested were above the New Hampshire guidance level.
7
Coliform bacteria
Recommended for every private well, every year.
8
Nitrate
Recommended for every private well, especially near farms or septic systems.
9
Volatile organic compounds (VOCs)
4 leaking underground storage tank sites on record locally.
10
PFAS
1 unlined landfill on record locally.
11
Metals panel
1 hazardous waste site on record locally.

Test your Henniker well for arsenic, fluoride and copper

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 $209 Already 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 Henniker numbers, $29. Every line explained, ranked by what matters, with the fix for each.

Wells in Henniker

550 domestic wells in Henniker are on record with the state since 1984. 99% are drilled into bedrock, and the typical well is 400 feet deep (one in ten goes past 640 feet).

In a typical Henniker well, bedrock starts about 80 feet down, the median yield is 5 gallons per minute, 24% 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.

163

1980s

1990s

156

2000s

2010s

2020s

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 Henniker

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 town 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.

Private Wells, NHDES
New Hampshire Environmental Laboratory Accreditation Program, NHDES

Contamination sources on record in Henniker

NHDES records 4 leaking underground storage tank sites, 1 unlined landfill, 1 hazardous waste site, and 3 reported spills and releases in Henniker, among 72 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.

4: leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
1: unlined landfillOlder unlined landfills are a leading source of PFAS, VOCs and metals in nearby wells.
1: hazardous waste siteSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
3: reported spills and releasesMost spills are fuel; a few are solvents or chemicals that reach the water table.
15: registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
12: locally identified potential contamination sourcesTowns inventory these (vehicle repair, labs, salt piles, farms) when they draw wellhead protection maps.
33: other remediation projects
3: other solid waste facilities

Treatment that fits the local profile

Arsenic

Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange

Copper

Neutralizing filter to raise pH; Point-of-use reverse osmosis

Lead

Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching

Radon

Aeration (bubble-up or diffused) whole-house; Granular activated carbon whole-house (lower levels only)

Sodium

Point-of-use reverse osmosis; Distillation

Fluoride

Point-of-use reverse osmosis; Activated alumina; Distillation

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 arsenic

Under-sink reverse osmosis system

under-sink or countertop, about $300

Look for NSF/ANSI 58 certification listing the contaminant you need removed.

For arsenic

Whole-house arsenic and uranium filter

whole-house, at the point of entry, about $2,500

Adsorptive iron-based media; sized to your well yield.

For arsenic

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 copper

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 Claryum 3-Stage under-sink filter

under-sink or countertop, about $175

Certified to NSF/ANSI 53 to reduce 99% of lead and 99.7% of PFOA and PFOS at the tap. Not a fix for arsenic, nitrate or bacteria.

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 Henniker

No water treatment company serves Henniker 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 Henniker, and you get an email naming it first.

Common questions

How deep are wells in Henniker?

The typical domestic well in Henniker is 400 feet deep, based on 550 wells reported to the state since 1984. One in ten is deeper than 640 feet. 99% are drilled into bedrock.

How often should I test a private well in Henniker?

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 near Henniker

Closest first. Groundwater does not stop at a line on a map, so the next town 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: 100 samples in Henniker. 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 Henniker, up to 221 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.
NH DHHS WISDOM private well summaries: modeled chance (28%) that a well in Henniker exceeds 5 ug/L of arsenic, from geology rather than tests. 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. Retrieved September 3, 2026.
NHDES Water Well Inventory: 586 well records in Henniker, 550 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: 72 regulated sites located in Henniker. 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.