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KnowYourWellWater

Maine Well Water

Last reviewed October 24, 2026

Overview

A large share of Maine households rely on private wells, many drilled into bedrock. Because private wells are not covered by the federal Safe Drinking Water Act, testing is the owner’s responsibility.

Hydrogeology & what it means

Much of Maine’s groundwater comes from fractured bedrock aquifers. Naturally occurring arsenic and uranium are well documented by the USGS and state agencies in parts of the state’s bedrock, and radon in water is a recognized concern in some areas.

Documented regional concerns

  • Naturally occurring arsenic in some bedrock wells (no taste or odor — only testing reveals it).
  • Uranium in some bedrock groundwater.
  • Radon in water in parts of the state.
  • Bacteria and nitrate, as with private wells everywhere.

These are documented possibilities, not a reading of your well

Regional geology tells you what to test for, not what your specific well contains. Only your own lab results can tell you that.

Frequently asked questions

How often should I test a private well in Maine?

At least annually for bacteria and nitrate, plus arsenic, uranium and radon at least once (and after any changes), using a state-accredited laboratory. Confirm current recommendations with the Maine CDC Drinking Water Program.