Guide · Updated 2026-08-31

Arsenic in Maine Well Water

Arsenic is common in Maine private wells and invisible in the glass. Get a certified-lab number before anyone sells you a tank.

A clear glass of Maine well water is not a test. Maine CDC’s brochure and arsenic tip sheet both say arsenic has no taste, smell, or color at the levels that show up in domestic wells. The only number that counts is a certified-lab result. This page does not interpret that number as a health score, does not design a system, and does not rank a brand.

Maine CDC’s private-well page — the same page wellwater.maine.gov redirects to — states that private wells are unregulated. Property owners are responsible for testing. EPA’s private-wells pages and CDC’s well-testing guidance say the same thing from the federal side: a kitchen tap on a private well is not a public water system.

Get a certified-lab arsenic result first

Start at this site’s Maine certified-lab inventory. Confirm the lab currently holds a drinking-water arsenic field on Maine CDC’s accreditation list. Accreditation is by analyte. A coliform certificate is not an arsenic certificate. Then call about bottles, the sample point (untreated kitchen cold), and how the lab reports units.

Maine CDC tells owners to test every year for coliform, E. coli, nitrate, and nitrite, and every 3–5 years for arsenic plus chloride, copper, fluoride, hardness, iron, lead, magnesium, manganese, pH, radon, sodium, and uranium. If you have never tested, CDC recommends a comprehensive or standard panel that includes that list. Other times CDC names: expecting a baby, a change in smell, taste, or color, a well that ran dry and came back, buying a home, after treatment work, or after well work.

A store kit is a screen. It does not replace a certified arsenic method. Well water test kits explains that split. If you want a mail-in panel while you wait on a Maine lab, Tap Score and SimpleLab are official public URLs labeled application pending. There is no tracking tag on those links. See the disclosure.

Bacteria or nitrate on the same sheet still goes to the health department, even on an arsenic page. Circle those lines first. Then read how to read a lab report.

Compare the number to Maine CDC’s MEG of 10 µg/L

Maine’s Tracking Network publishes Maximum Exposure Guidelines for private-well summaries. The arsenic MEG is 10 µg/L (micrograms per liter). That is the private-well comparison number on this page.

EPA’s Arsenic Rule (2001, public-system compliance 2006) set a public-water-system MCL of 10 ppb, which is the same concentration as 10 µg/L or 0.010 mg/L. That MCL is a Safe Drinking Water Act limit for community and non-transient non-community systems. Private wells are not under that Act. Do not call 10 µg/L a private-well legal limit. It is the MEG Maine CDC uses, and it matches the public-system number people already know.

Units trip people. µg/L is ppb. If the lab reports 0.010 mg/L, that is 10 µg/L. If the lab reports 10 mg/L, something is wrong — that is a thousand times the MEG. If the reporting limit sits at or above 10 µg/L, you bought a test that cannot tell you whether you are under the MEG. Ask for a lower reporting limit.

If the sheet is at or above 10 µg/L, or you do not understand it, call Maine CDC Toxicology: 866-292-3474 (toll-free in Maine) or 207-287-4311, TTY Maine Relay 711, or email ehu@maine.gov. That is the number on the private-well page and on the tip sheet for “too much arsenic” or “not sure you understand.” This site will not turn the line into a risk score.

What “about 1 in 10” means — and what a town map does not

USGS Scientific Investigations Report 2010–5199 (Nielsen, Lombard, and Schalk), prepared with Maine CDC, states that prior studies established approximately 10 percent of domestic wells in Maine have arsenic greater than the EPA MCL of 10 µg/L. The HETL 2005–09 set they organized had 11,111 wells in 531 towns. It was a convenience sample of owner-submitted bottles, not a random sample, and USGS says it may not be representative of all wells in a given area.

In that set, more than 25 percent of sampled wells in 44 towns exceeded 10 µg/L. USGS describes clusters in southern coastal Maine, the Kennebec County area, and Ellsworth / Hancock. Maine CDC’s brochure uses the same “1 in 10 wells” line. The tip sheet adds that there are wells high in arsenic in all parts of Maine.

Maine Tracking Network warns that HETL results are owner-submitted and spatially biased: for contaminants that cluster, such as arsenic, “hot spot” towns may test more, so the percent above the guideline in those towns is likely biased upward. Repeat that when you open a town or county map. Do not rank towns as “worst.” Do not tell a neighbor their town is safe or unsafe from a map. Your well is a hole in the rock, not a town average.

Low-income kit and help-paying mail — we do not run either

Maine CDC’s Well Water Information Request form will mail a list of certified labs. The same form lets you check a box for mailed information on help paying for arsenic treatment systems. Low-income Maine residents who are eligible for MaineCare, SNAP, TANF, or other benefit programs can request a free HETL test kit on that form. Maine CDC may confirm eligibility through benefit enrollment lists. This site does not collect eligibility, does not mail kits, and does not invent a rebate program. Use the form.

The CDC brochure also tells people who cannot afford treatment to call MaineHousing (800-452-4668 or Maine Relay 711) or visit mainehousing.org. That is CDC’s pointer, not a Well Diagnosis program.

Treatment class only after a sheet

Do not shop a tank because a map is orange. After you have a number, Maine CDC’s Drinking Water Program (April Bledsoe, 207-215-7124, april.bledsoe@maine.gov) is the free technical-assistance line for treatment types, sampling, and well questions. Toxicology is the line for what the number means.

Classes people ask about for arsenic — reverse osmosis, adsorptive media, and anion exchange — are classes to take to that program or to a licensed installer, not a shopping list on this page. Look up a model in the NSF drinking-water treatment unit database. NSF is a claim on a model, not a badge this site awards. Do not rank brands. Do not install anything “for arsenic” until the treatment order after the pressure tank makes sense for the rest of the sheet (iron, hardness, sediment). A fouled bed is how an arsenic class fails.

If bacteria is present, stop. Health department first. An arsenic cartridge on a contaminated well is the wrong Monday.

Dated notes, not a shopper

Maine lab news lives at /labs/maine/news. Public-system PFAS proposals on that page do not change the arsenic MEG. The certified-labs index is /certified-labs-by-state. The homepage is for stains and smells after you have a sheet.

Bottom line

Arsenic is common in Maine private wells and invisible in the glass. Order a certified-lab arsenic test from the Maine inventory. Compare µg/L to Maine CDC’s MEG of 10. If you are at or above that number, or you cannot read the units, call Maine CDC Toxicology. Treatment class comes after the sheet. Bacteria and nitrate still go to the health department.