State Well Water Guide
Maine Private Well Water Guide
Nearly half of Maine residents — over 650,000 people — rely on private wells drilled into or dug from Maine's ancient granite and metamorphic bedrock. Maine has some of the highest naturally occurring arsenic concentrations in New England, with approximately 10% of tested private wells exceeding the EPA limit of 10 ppb. Radon dissolved in water (distinct from airborne radon) is also prevalent statewide. The Maine Center for Disease Control & Prevention (MECDC) recommends all new and existing wells be tested comprehensively, and retested after any flood or nearby construction.
Testing Guidance
Maine DHHS recommends testing private wells at minimum annually for coliform bacteria and nitrates. Additionally, test for arsenic and radon in water every 3–5 years (or immediately for newly purchased homes). If your home was built before 1986, test for lead. Wells near agricultural land should be tested for arsenic, atrazine, and nitrates. Wells within 1 mile of former military airfields (Loring AFB, Brunswick Naval Air Station) should be tested for PFAS.
What to Test For in Maine
Total coliform bacteria and E. coli — annual minimum, all wells
Arsenic — all wells; naturally elevated statewide from granite bedrock
Radon in water — widespread from granite; 5,000+ pCi/L common in some counties
Uranium — granitic regions; often co-elevated with arsenic
Nitrates — wells near agriculture, septic systems, or coastal development
Lead — homes built before 1986; old pump heads, pressure tanks, and plumbing
PFAS — wells within 2 miles of Loring AFB (Aroostook County) or Brunswick Naval Air Station
Manganese — glacial till wells; elevated concentrations documented in many Maine counties
Common Contamination Risks in Maine
Naturally occurring arsenic from bedrock — approximately 10% of Maine private wells exceed the EPA MCL of 10 ppb; highest concentrations in southwestern and south-central Maine
Radon dissolved in groundwater from granite — Maine has among the highest radon-in-water levels in the U.S.; radon is released into indoor air when using tap water
Uranium from granitic geology — co-occurs with arsenic in many bedrock wells; health concern at chronic exposure levels
PFAS contamination near former military bases — Loring AFB and Brunswick Naval Air Station both had AFFF firefighting foam programs with documented groundwater impacts
Coliform bacteria from poorly sealed or shallow dug wells — risk increases after heavy rainfall or flooding
Manganese from glacial till sediments — linked to neurodevelopmental effects in children at elevated concentrations
Contaminant Guides Relevant to ME Wells
PFAS
Synthetic Chemicals
EPA limit: 4 ppt
Lead
Heavy Metals
EPA limit: 15 ppb (action level)
Nitrates
Agricultural Chemicals
EPA limit: 10 mg/L
DBPs
Disinfection Byproducts
EPA limit: 80 µg/L (TTHMs) / 60 µg/L (HAA5)
Arsenic
Heavy Metals
EPA limit: 10 ppb
Hard Water
Minerals
EPA limit: No federal limit
Chlorine
Disinfection Chemicals
EPA limit: 4 mg/L (MRDL)
Microplastics
Emerging Contaminants
EPA limit: No federal limit
Bacteria
Microbial Contamination
EPA limit: Zero E. coli / < 1 coliform per 100 mL
Fluoride
Minerals
EPA limit: 4 mg/L (MCL) / 2 mg/L (Secondary MCL)
Chromium-6
Heavy Metals
EPA limit: 100 ppb (total chromium)
Copper
Heavy Metals
EPA limit: 1.3 mg/L (action level)
Radon
Radioactive Contaminants
EPA limit: No finalized MCL
Iron & Manganese
Minerals
EPA limit: 0.3 mg/L iron / 0.05 mg/L manganese (aesthetic SMCLs)
Atrazine
Agricultural Chemicals
EPA limit: 3 ppb (0.003 mg/L)
Uranium
Radioactive Contaminants
EPA limit: 30 µg/L (30 ppb)
Perchlorate
Industrial Chemicals
EPA limit: 0.056 mg/L (56 ppb)
VOCs
Industrial Chemicals
EPA limit: Varies by compound: benzene 5 ppb; TCE 5 ppb; PCE 5 ppb; vinyl chloride 2 ppb
Radium
Radioactive Contaminants
EPA limit: 5 pCi/L (combined Ra-226 + Ra-228)
Crypto & Giardia
Microbial Contamination
EPA limit: Zero (treatment technique standard)
Hydrogen Sulfide
Naturally Occurring Compounds
EPA limit: No MCL; Secondary MCL (aesthetic) of 0.05 mg/L
Selenium
Minerals
EPA limit: 50 ppb (0.05 mg/L)
Cadmium
Heavy Metals
EPA limit: 5 ppb (0.005 mg/L)
Mercury
Heavy Metals
EPA limit: 2 ppb (0.002 mg/L)
Barium
Heavy Metals
EPA limit: 2 mg/L
Find a Certified Lab in Maine
Use the Maine state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
ME Certified Lab Directory ↗Maine Well Water FAQs
Related Pages
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.
Quick Reference
State program
ME Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
ME Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides