Well water in Madison, New Hampshire
In Madison, 27% of 34 private wells tested between 2006 and 2020 had copper above the New Hampshire guidance level (1.3 mg/L), according to NH DHHS.
65 private wells tested 2006 to 2020 in state summaries; 21 individual samples from 19 wells, 1986 to 2022. Data refreshed September 3, 2026.
Separately, a USGS and NHDES statistical model puts the chance that a bedrock well in Madison exceeds 5 ug/L of arsenic at 7% (as low as 1% 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 | Wells tested | Above state level | Median | 95th pct | Highest | State level | |
|---|---|---|---|---|---|---|---|
| Copper (stagnant) | 34 | 27% | 0.1 | 2.7 | 6 | 1.3 mg/L | |
| Uranium | 49 | 25% | 8 | 111 | 420 | 30 ug/L | |
| Iron | 40 | 23% | 100 | 900 | 2,500 | 300 ug/L | |
| Sodium | 39 | 21% | 6.8 | 38.6 | 47.5 | 20 mg/L | |
| Lead (stagnant) | 36 | 17% | 3.7 | 42.5 | 122 | 15 ug/L | |
| Manganese | 40 | 5% | 0 | 100 | 1,000 | 300 ug/L | |
| Fluoride | 65 | 5% | 0.6 | 3.3 | 5.8 | 4 mg/L | |
| Chloride | 44 | 0% | 4.3 | 72.1 | 180 | 250 mg/L | |
| Nitrate | 42 | 0% | 0.1 | 1.6 | 1.8 | 10 mg/L | |
| Nitrite | 42 | 0% | 0 | 0 | 0 | 1 mg/L | |
| Arsenic | 40 | 0% | 0.7 | 0.8 | 3.4 | 5 ug/L |
What individual samples found
Each row summarizes every public sample for that contaminant inside Madison. 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 | |
|---|---|---|---|---|---|---|---|
| Nitrate 1986 to 2021 | 21 | 62% | 0% | 0.19 | 1.3 | 10 mg/L EPA limit | |
| Fluoride 1988 to 2021 | 18 | 89% | 0% | 1.15 | 2.8 | 4 mg/L EPA limit | |
| Manganese 1988 to 2022 | 20 | 40% | no limit | 0 | 40 | 300 ug/L health guideline | |
| Chloride 1986 to 2021 | 18 | 50% | no limit | 1 | 55 | 250 mg/L nuisance level | |
| Sodium 1988 to 2021 | 16 | 88% | no limit | 5.5 | 33.5 | 20 mg/L health guideline |
Sampled fewer than 10 times, too few to summarize: Uranium (5), Lead (9), Arsenic (9), Copper (8), Radon (1).
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What this means
Among homeowners in Madison who sent a sample to the state lab, the health-based limits most often exceeded were copper (27% of 34 wells), uranium (25% of 49 wells), and lead (17% of 36 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 and sodium 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 Madison
- PFAS1 unlined landfill on record locally.
- Volatile organic compounds (VOCs)1 unlined landfill on record locally.
- Metals panel1 hazardous waste site on record locally.
- Copper27% of 34 local wells tested were above the New Hampshire guidance level.
- Uranium25% of 49 local wells tested were above the New Hampshire guidance level.
- Iron23% of 40 local wells tested were above the New Hampshire guidance level.
- Sodium21% of 39 local wells tested were above the New Hampshire guidance level.
- Lead17% of 36 local wells tested were above the New Hampshire guidance level.
- Manganese5% of 40 local wells tested were above the New Hampshire guidance level.
- Fluoride5% of 65 local wells tested were above the New Hampshire guidance level.
- Coliform bacteriaRecommended for every private well, every year.
Wells in Madison
606 domestic wells in Madison are on record with the state since 1984. 75% are drilled into bedrock, and the typical well is 382 feet deep (one in ten goes past 720 feet).
In a typical Madison well, bedrock starts about 50 feet down, the median yield is 10 gallons per minute, 18% 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 Madison
NHDES records 1 unlined landfill, 1 hazardous waste site, and 2 reported spills and releases in Madison, among 45 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.
- 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.
- 2
- reported spills and releasesMost spills are fuel; a few are solvents or chemicals that reach the water table.
- 8
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 5
- locally identified potential contamination sourcesTowns inventory these (vehicle repair, labs, salt piles, farms) when they draw wellhead protection maps.
- 27
- other remediation projects
- 1
- other solid waste facility
Treatment that fits the local profile
- Copper
- Neutralizing filter to raise pH; Point-of-use reverse osmosis
- Uranium
- Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
- Lead
- Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching
- Iron
- Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
- Sodium
- Point-of-use reverse osmosis; Distillation
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
Book a free water test in Madison
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 Madison?
The typical domestic well in Madison is 382 feet deep, based on 606 wells reported to the state since 1984. One in ten is deeper than 720 feet. 75% are drilled into bedrock.
Is there arsenic in well water in Madison?
Arsenic was detected in 22% of 9 public well samples in Madison, 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 Madison?
The median radon level across 1 public samples in Madison was 6,900 pCi/L, with a high of 6,900 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Madison?
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.
Sources
- USGS Water Quality Portal: 125 samples in Madison. 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 11 contaminants in Madison, up to 65 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: 644 well records in Madison, 606 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: 45 regulated sites located in Madison. 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.