Well water in Massachusetts
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Testing strongly recommended
tested well samples in Massachusetts exceeded the EPA limit for PFOS (4 ng/L), based on public data from USGS Water Quality Portal.
1,793 private wells tested 2020 to 2023 in state summaries; 44,013 test results across 15 contaminants from at least 2,255 wells, 1944 to 2025; nitrate has the most at 12,883. Data refreshed September 16, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
MassDEP offered free PFAS tests to towns without public water and to wells near suspected sources such as landfills, fire stations and airports, so these shares describe the wells that took part rather than every well in town.
An estimated 615,948 people in Massachusetts get their drinking water from a private well, per USGS 2015 county water use.
Separately, the USGS national arsenic model estimates that 5% of the 615,948 people on private wells in Massachusetts draw water above 10 ug/L (the model's range is 4% to 7%), from geology and well depth rather than local tests.
What homeowner tests found
MassDEP Private Well PFAS Sampling Program: private wells tested and reported to the state, 2020 to 2023. 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 Massachusetts. 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 |
|---|---|---|---|---|---|---|
| PFOS 2019 to 2021 | 153 | 80% | 47 | 20,800 | 4 ng/L EPA limit | |
| PFOA 2019 to 2021 | 153 | 85% | 11 | 13,700 | 4 ng/L EPA limit | |
| Nitrate 1944 to 2025 | 12,883 | 87% | 1.3 | 330 | 10 mg/L EPA limit | |
| Arsenic 1976 to 2023 | 730 | 61% | 0.225 | 620 | 10 ug/L EPA limit | |
| E. coli 2002 to 2019 | 43 | 2% | 0 | 2 | 0 MPN/100mL EPA limit | |
| Lead 1976 to 2023 | 1,006 | 40% | 0 | 40 | 15 ug/L EPA limit | |
| Radium (226 + 228) 1995 to 2019 | 172 | 76% | 0 | 6 | 5 pCi/L EPA limit | |
| Uranium 1957 to 2019 | 362 | 58% | 0.028 | 150 | 30 ug/L EPA limit | |
| Fluoride 1948 to 2023 | 2,808 | 59% | 0.03 | 13 | 4 mg/L EPA limit | |
| Copper 1953 to 2023 | 1,014 | 48% | 0 | 0.691 | 1.3 mg/L EPA limit | |
| Chloride 1944 to 2023 | no limit | 9,288 | 100% | 18 | 20,000 | 250 mg/L nuisance level |
| Sodium 1952 to 2023 | no limit | 8,098 | 100% | 11 | 3,640 | 20 mg/L health guideline |
| Iron 1948 to 2019 | no limit | 3,961 | 78% | 38 | 260,000 | 300 ug/L nuisance level |
| Manganese 1952 to 2023 | no limit | 3,272 | 92% | 48.8 | 54,000 | 300 ug/L health guideline |
| Radon 1992 to 2014 | no limit | 70 | 100% | 750 | 22,400 | 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 |
|---|---|---|---|---|
| Nitrate | 14%5,848 samples | 4%1,749 samples | 23%2,296 samples | 19%2,990 samples |
| Fluoride | <1%2,435 samples | 0%99 samples | 0%253 samples | 0%21 samples |
| Copper | 0%637 samples | 0%154 samples | 0%221 samples | n/a |
| Lead | 3%597 samples | 0%173 samples | <1%234 samples | n/a |
| Arsenic | 6%356 samples | 2%151 samples | 7%221 samples | n/a |
| Uranium | 0%47 samples | 0%94 samples | <1%221 samples | n/a |
Arsenic above the limit in Massachusetts rose from 2% of 151 samples in the 2000s to 7% of 221 in the 2010s.
Nitrate, fluoride, copper, lead, uranium have held within a few points between the two most recent periods with enough samples.
What this means
Among homeowners in Massachusetts who sent a sample to the state lab, the health-based limits most often exceeded were PFOA (19% of 1,793 wells), PFOS (10% of 1,793 wells), and PFHxS (<1% of 1,793 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 Massachusetts
- 1PFOS73% of 153 local samples were above the limit.
- 2PFOA68% of 153 local samples were above the limit.
- 3Nitrate15% of 12,883 local samples were above the limit.
- 4Arsenic6% of 730 local samples were above the limit.
- 5E. coli2% of 43 local samples were above the limit.
- 6Lead2% of 1,006 local samples were above the limit.
- 7PFHxS<1% of 1,793 local wells tested were above the EPA limit.
- 8Radium (226 + 228)<1% of 172 local samples were above the limit.
- 9PFAS527 unlined landfills on record locally.
- 10Volatile organic compounds (VOCs)527 unlined landfills on record locally.
- 11Metals panel1,025 hazardous waste sites on record locally.
Test your Massachusetts well for PFOS, PFOA and nitrate
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.
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Where to get a well tested in Massachusetts: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Massachusetts numbers, $29. Every line explained, ranked by what matters, with the fix for each.
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Send me the Massachusetts report
The numbers above, which tests to order and where, and the treatment that fits the local profile, in one email.
Wells in Massachusetts
80,019 domestic wells in Massachusetts are on record with the state since 1914. 78% are drilled into bedrock, and the typical well is 265 feet deep (one in ten goes past 523 feet).
In a typical Massachusetts well, bedrock starts about 21 feet down, the median yield is 9 gallons per minute, 10% 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 MassDEP Well Location Viewer and choose Water Well.
- The completion report lists total depth, depth to bedrock, static water level, yield and the driller.
Drillers have filed completion reports with the state since 1984; the viewer's public copy is refreshed a few times a year.
The rock under Massachusetts
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 Massachusetts
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, MassDEP
- Certified Laboratories, MassDEP
Contamination sources on record in Massachusetts
MassDEP records 527 unlined landfills and 1,025 hazardous waste sites in Massachusetts, among 6,660 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.
- 527
- unlined landfillsOlder unlined landfills are a leading source of PFAS, VOCs and metals in nearby wells.
- 1,025
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 3,772
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 77
- lined landfills and transfer facilities
- 1,259
- other remediation projects
Treatment that fits the local profile
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
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
E. coli
Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system
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 PFOA
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
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 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 PFOS
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 PFOS
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.
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.
Common questions
How deep are wells in Massachusetts?
The typical domestic well in Massachusetts is 265 feet deep, based on 80,019 wells reported to the state since 1914. One in ten is deeper than 523 feet. 78% are drilled into bedrock.
Is there arsenic in well water in Massachusetts?
Arsenic was detected in 61% of 730 public well samples in Massachusetts, and 6% 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 Massachusetts?
The median radon level across 70 public samples in Massachusetts was 750 pCi/L, with a high of 22,400 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Massachusetts?
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 Massachusetts
- Barnstable11% pfoa
- Berkshire1% pfoa
- Bristol23% pfoa
- Dukes14% pfoa
- Essex30% pfoa
- Franklin8% pfoa
- Hampden6% pfoa
- Hampshire10% pfoa
- Middlesex46% pfoa
- Nantucket23% pfoa
- Norfolk5% nitrate
- Plymouth25% pfoa
- Worcester20% pfoa
1 counties have fewer than 30 public samples and are included in the Massachusetts totals above rather than shown separately: Suffolk.
Want the numbers themselves? Download the Massachusetts dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 44,013 samples in Massachusetts. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- MassDEP Private Well PFAS Sampling Program: summaries for 4 contaminants in Massachusetts, up to 1,793 wells each. Private well PFAS results from the Massachusetts Department of Environmental Protection free sampling program, 2020 to 2023, one anonymized row per well. Shares are against the EPA limit for each compound (4 ng/L for PFOA and PFOS, 10 ng/L for PFHxS and PFNA). Massachusetts applies its own PFAS6 standard of 20 ng/L to the sum of six compounds; that sum is not a contaminant page here. Zero means not detected. Retrieved September 16, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 615,948 people on private wells in Massachusetts 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.
- MassDEP well completion reports: 126,929 well records in Massachusetts, 80,019 domestic. Well completion reports filed with the Massachusetts Department of Environmental Protection, as published in the Well Location Viewer (April 2023 vintage). Only aggregates are shown; owner names and addresses are never stored. Retrieved September 16, 2026.
- MassDEP regulated sites: 6,660 regulated sites located in Massachusetts. Chapter 21E release sites, solid waste landfills and underground storage tank facilities from the Massachusetts Department of Environmental Protection, through MassGIS. Retrieved September 16, 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.