Maine Well Water Testing: Arsenic, PFAS, Uranium, and What to Test For

Maine has the highest percentage of residents relying on private well water in the northeastern United States. Roughly half of all homes in the state pull their drinking water from groundwater rather than municipal supplies — which means the biological and chemical quality of that water is entirely the homeowner's responsibility to monitor.

The bedrock geology underneath Maine's landscape is not neutral ground. Granite formations naturally release arsenic, uranium, and radon into groundwater. Agricultural and military land uses have left PFAS contamination in aquifers across the state. Buying a home with a private well without testing that water is not an acceptable risk, and the mortgage underwriting process for most loan types requires testing anyway. The question is knowing what to test, not whether to test.

Why Maine's Well Water Is Complicated

The issue starts underground. Southern and coastal Maine sit atop granite formations that naturally release arsenic and uranium into groundwater as the rock slowly weathers. These are not contamination events — they are geological features. Roughly 1 in 10 private wells in Maine contains arsenic levels that exceed the federal EPA limit of 10 micrograms per liter. Concentrations are highest in York, Cumberland, Androscoggin, and Sagadahoc counties, though elevated levels appear statewide.

Uranium co-occurs with arsenic in many of the same geological zones. It is a nephrotoxin — chronic exposure damages kidney function. Manganese, which can cause neurological issues with long-term consumption at elevated levels, is another common co-contaminant.

Radon adds a different dimension. Because Maine's bedrock produces high levels of radon gas through uranium decay, the gas dissolves in well water and then releases into household air when water is aerated — during showers, dishwashing, and laundry. Waterborne radon is distinct from soil-gas radon that enters through foundation cracks, and the two issues require separate testing and separate mitigation systems.

The PFAS layer is a third concern. The Maine DEP is actively investigating more than 700 sites across the state where treated municipal sludge was spread on agricultural fields over decades — a once-common practice that contaminated local aquifers with per- and polyfluoroalkyl substances. PFAS contamination is documented near former military installations, including areas associated with Navy Base Brunswick, and in farming communities across central Maine. PFAS are synthetic compounds that do not break down in the environment or in the human body, accumulating over time.

What Each Loan Program Requires

Your mortgage type determines which water test panel is required before closing. Standard panels often exclude arsenic and PFAS — a significant gap given Maine's geology.

The USDA Rural Development Set RD panel's exclusion of arsenic is a well-documented gap. If you are using a USDA loan, the lender's required test will not check for arsenic. Pay for a supplemental arsenic test yourself — it costs roughly $25 to $40 at a certified lab. Do not skip it.

None of the standard required panels include PFAS. If the property is located near agricultural land, a former military base, or an area with documented sludge application history, budget for a PFAS panel separately. Specialized PFAS testing runs $150 to $500 depending on the lab and the number of compounds tested.

The Contaminants and What Treatment Costs

Arsenic

Testing: Free through Maine CDC's private well testing program (mail-in kit), or $25–$40 at a private certified lab.

Treatment: Two main technologies depending on concentration and household budget.

• Point-of-use reverse osmosis (RO): A countertop or under-sink RO system removes arsenic from drinking water only. Installation and unit cost ranges from $250 to $800. Annual membrane and filter replacement costs roughly $150 to $300. Does not treat shower or bathing water.
• Whole-house anion exchange system: Treats all water entering the house. Installation costs $2,500 to $8,000 depending on system size. Annual media replacement and maintenance runs $300 to $500. Required if arsenic levels are high and full-household treatment is needed for health or loan approval reasons.

Seller credit negotiation: If the test reveals elevated arsenic, the standard approach is to request a seller credit at the purchase price sufficient to cover the installation of a treatment system, rather than asking the seller to install it themselves before closing (which rarely goes smoothly on timeline).

Radon in Water

Testing: Combined air-and-water radon dual-test packages run approximately $70 through certified labs. Maine has certified radon testing resources through the state's radon program.

Treatment: Depends on radon concentration in the water.

• Low-to-moderate levels: Granular activated carbon (GAC) filter. Installation cost $2,000 to $4,000. The carbon media absorbs radon, but must be replaced regularly (and disposed of as low-level radioactive waste) — annual cost around $600.
• High levels: Active aeration system that sprays water through a tank and vents radon gas outdoors. More effective for high concentrations. Installation cost approximately $5,000 to $8,000. Annual service around $300.

If indoor air radon levels (from soil gas, separate from the water) exceed the EPA action level of 4.0 pCi/L, a sub-slab depressurization system for the foundation is the standard fix — typically $1,200 to $2,500 installed. Air radon and water radon are separate problems requiring separate solutions.

Uranium and Manganese

Both are tested through Set A (conventional) and Set B (MaineHousing/VA) panels. If your required panel does not include uranium, it can be added to a supplemental panel for $25 to $50 at most certified labs.

Uranium treatment: Anion exchange or reverse osmosis. Often the same system that addresses arsenic will also reduce uranium.

Manganese treatment: Oxidation filtration (greensand filter or similar). Installation $1,500 to $4,000 depending on concentration and system.

One exchange from r/Maine captures the real-world outcome: a homeowner installed both a reverse osmosis system for arsenic and uranium and an active aeration system for waterborne radon — total expenditure exceeding $10,000 — after closing. Testing before closing and negotiating a seller credit would have put those costs on the seller's side of the transaction.

PFAS

PFAS are a special case. Unlike arsenic and radon, there is no naturally occurring geological source of PFAS — it always traces back to a human-generated contamination event. If your property is in a potential PFAS zone, test early.

Specialized PFAS panels testing for the full suite of regulated compounds cost $150 to $500 at certified labs. The Maine DEP maintains a database of documented contamination sites. Checking proximity to mapped sludge application fields or military installations is worth doing before ordering a property if you are looking in central or downeast Maine.

Treatment: Specialized granular activated carbon systems or dual-stage anion exchange specifically designed for PFAS. Installation cost ranges from $3,000 to $8,000. Annual media replacement (which must be disposed of as hazardous waste given the PFAS loading) costs $700 to $1,200.

The Bottom Line on Timing

The inspection contingency window — typically 7 to 14 days — is when water testing must happen. Labs require several days to return results. Order the water test on the same day you schedule your general home inspection, not after.

If results come back with elevated contaminants, your attorney uses those findings to draft an inspection addendum requesting a seller credit or remediation. If the seller refuses and the contamination is serious enough, you have grounds to terminate and recover your earnest money before the contingency expires.

Water quality is not a cosmetic issue. It affects the habitability of the home, the cost of ownership for years afterward, and potentially your family's health. Budget the cost of a comprehensive test panel as part of the due diligence line item from day one.

The Maine First-Time Home Buyer Guide includes a well water inspection checklist, guidance on which contaminants to test for based on the property's location, and a framework for using test results in purchase price negotiations.

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