Well water in Maine
1in6
Testing recommended
private wells tested in Maine had arsenic above the Maine guideline (10 ug/L), according to Maine CDC.
31,960 private wells tested in state summaries; 22,646 test results across 17 contaminants from at least 3,567 wells, 1941 to 2026; PFOA has the most at 3,567. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
Maine DEP samples private wells near fields where sludge or septage was spread and near other known PFAS sources, and resamples detections. PFAS shares describe wells that were tested for a reason, not every well in the area. In that targeted sampling, 19% of 3,567 PFOA results in Maine were above the EPA limit of 4 ng/L. In that targeted sampling, 11% of 3,567 PFOS results in Maine were above the EPA limit of 4 ng/L.
An estimated 660,497 people in Maine get their drinking water from a private well, per USGS 2015 county water use.
Separately, the USGS national arsenic model estimates that 16% of the 660,497 people on private wells in Maine draw water above 10 ug/L (the model's range is 12% to 20%), from geology and well depth rather than local tests.
What homeowner tests found
Maine Tracking Network private well summaries: private wells tested and reported to the state. 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.
What individual samples found
Each row summarizes every public sample for that contaminant inside Maine. 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 |
|---|---|---|---|---|---|---|
| Arsenic 1977 to 2023 | 528 | 89% | 20 | 3,000 | 10 ug/L EPA limit | |
| PFOA 2017 to 2026 | 3,567 | 58% | 0.396 | 7,590 | 4 ng/L EPA limit | |
| PFOS 2017 to 2026 | 3,567 | 44% | 0 | 17,200 | 4 ng/L EPA limit | |
| Uranium 1958 to 2023 | 227 | 82% | 1.16 | 960 | 30 ug/L EPA limit | |
| Nitrate 1941 to 2023 | 2,065 | 78% | 0.39 | 162 | 10 mg/L EPA limit | |
| PFNA 2017 to 2026 | 3,566 | 16% | 0 | 1,830 | 10 ng/L EPA limit | |
| PFHxS 2017 to 2026 | 3,562 | 30% | 0 | 489 | 10 ng/L EPA limit | |
| Radium (226 + 228) 1958 to 2019 | 112 | 89% | 0 | 57 | 5 pCi/L EPA limit | |
| Lead 1977 to 2023 | 297 | 42% | 0 | 30 | 15 ug/L EPA limit | |
| Fluoride 1948 to 2023 | 862 | 66% | 0.1 | 4.9 | 4 mg/L EPA limit | |
| Copper 1953 to 2023 | 187 | 67% | 0 | 0.63 | 1.3 mg/L EPA limit | |
| E. coli 2011 to 2019 | 59 | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Chloride 1941 to 2023 | no limit | 1,169 | 99% | 9.13 | 2,020 | 250 mg/L nuisance level |
| Iron 1942 to 2023 | no limit | 1,011 | 85% | 100 | 880,000 | 300 ug/L nuisance level |
| Manganese 1949 to 2023 | no limit | 986 | 79% | 36.0 | 55,000 | 300 ug/L health guideline |
| Sodium 1953 to 2023 | no limit | 835 | 100% | 9 | 1,160 | 20 mg/L health guideline |
| Radon 1999 to 2014 | no limit | 46 | 100% | 2,020 | 102,000 | 2,000 pCi/L health guideline |
Over time
Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.
| Contaminant | before 2000 | 2000s | 2010s | 2020s |
|---|---|---|---|---|
| PFOA | n/a | n/a | 30%20 samples | 19%3,547 samples |
| PFOS | n/a | n/a | 25%20 samples | 11%3,547 samples |
| PFNA | n/a | n/a | 0%15 samples | 2%3,551 samples |
| PFHxS | n/a | n/a | 7%15 samples | 1%3,547 samples |
| Nitrate | 5%965 samples | 8%698 samples | 12%396 samples | n/a |
| Fluoride | <1%543 samples | 0%194 samples | 0%122 samples | n/a |
PFOA above the limit in Maine fell from 30% of 20 samples in the 2010s to 19% of 3547 in the 2020s.
PFOS above the limit in Maine fell from 25% of 20 samples in the 2010s to 11% of 3547 in the 2020s.
Nitrate, fluoride have held within a few points between the two most recent periods with enough samples.
What this means
Among homeowners in Maine who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (17% of 27,616 wells), uranium (7% of 23,366 wells), and fluoride (2% of 31,960 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.
What to test for in Maine
- 1Arsenic56% of 528 local samples were above the limit.
- 2PFOA19% of 3,567 local samples were above the limit.
- 3PFOS11% of 3,567 local samples were above the limit.
- 4Uranium10% of 227 local samples were above the limit.
- 5Nitrate7% of 2,065 local samples were above the limit.
- 6Fluoride2% of 31,960 local wells tested were above the Maine guideline.
- 7PFNA2% of 3,566 local samples were above the limit.
- 8PFHxS1% of 3,562 local samples were above the limit.
- 9Volatile organic compounds (VOCs)1,177 leaking underground storage tank sites on record locally.
- 10PFAS500 unlined landfills on record locally.
- 11Metals panel570 hazardous waste sites on record locally.
Test your Maine well for arsenic, PFOA and PFOS
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 Maine: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Maine numbers, $29. Every line explained, ranked by what matters, with the fix for each.
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Send me the Maine report
The numbers above, which tests to order and where, and the treatment that fits the local profile, in one email.
Wells in Maine
90,708 domestic wells in Maine are on record with the state since 1970. 98% are drilled into bedrock, and the typical well is 240 feet deep (one in ten goes past 455 feet).
In a typical Maine well, bedrock starts about 15 feet down, the median yield is 6 gallons per minute, 22% 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.
The rock under Maine
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 state centroid. A single well can sit in a different unit, especially near a boundary.
Official help in Maine
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 Well Water, Maine CDC
- Laboratory Accreditation, Maine CDC
Contamination sources on record in Maine
Maine DEP records 1,177 leaking underground storage tank sites, 500 unlined landfills, and 570 hazardous waste sites in Maine, among 4,871 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.
- 1,177
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 500
- unlined landfillsOlder unlined landfills are a leading source of PFAS, VOCs and metals in nearby wells.
- 570
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 2,624
- other remediation projects
Treatment that fits the local profile
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Uranium
Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
PFOA
Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
PFOS
Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
Nitrate
Point-of-use reverse osmosis; Anion exchange; 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 PFOA
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 PFOA
Whole-house PFAS carbon system
whole-house, at the point of entry, about $3,000
Granular activated carbon certified to NSF/ANSI 53 for PFOA and PFOS; replace media on schedule.
For PFOA
Aquasana HealthShield whole-house filter
whole-house, at the point of entry, about $2,099
Whole-house carbon system the maker certifies to reduce PFAS (PFOA and PFOS) and VOCs at every tap; a UV option adds bacteria protection.
Common questions
How deep are wells in Maine?
The typical domestic well in Maine is 240 feet deep, based on 90,708 wells reported to the state since 1970. One in ten is deeper than 455 feet. 98% are drilled into bedrock.
Is there arsenic in well water in Maine?
Arsenic was detected in 89% of 528 public well samples in Maine, and 56% 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 Maine?
The median radon level across 46 public samples in Maine was 2,020 pCi/L, with a high of 102,000 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Maine?
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.
Counties in Maine
Want the numbers themselves? Download the Maine dataset as CSV, every county and town, with the sources named.
Sources
- Maine DEP PFAS investigation: 14,254 samples in Maine. PFAS results for private wells sampled by the Maine Department of Environmental Protection. Retrieved September 3, 2026.
- USGS Water Quality Portal: 8,392 samples in Maine. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- Maine Tracking Network private well summaries: summaries for 6 contaminants in Maine, up to 31,960 wells each. Town summaries of private well tests run by the Maine Health and Environmental Testing Laboratory, published by Maine CDC through the Maine Tracking Network. Shares are against Maine's guideline for each analyte (arsenic 10 ug/L, uranium 30 ug/L, fluoride 2 mg/L, manganese 0.3 mg/L, nitrate 10 mg/L, nitrite 1 mg/L). Towns with too few tests are suppressed (NR). Only the share above the guideline and wells tested are published; no medians. Retrieved September 3, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 660,497 people on private wells in Maine 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.
- Maine Geological Survey well database: 95,597 well records in Maine, 90,708 domestic. Well construction records reported to the Maine Geological Survey by licensed well drillers. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 3, 2026.
- Maine DEP regulated sites: 4,871 regulated sites located in Maine. Remediation sites, leaking underground storage tanks and closed municipal landfills from the Maine Department of Environmental Protection. 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.