Montana Well Water
Last reviewed October 29, 2026
Overview
Private wells supply water to many Montana households. Because they are generally not regulated like public systems under the federal Safe Drinking Water Act, testing and wellhead protection are the owner’s responsibility.
Hydrogeology & what it means
Montana draws from alluvial valley aquifers and bedrock aquifers. The documented regional concerns below indicate what is worth testing for — not what any individual well contains.
Documented regional concerns
- Naturally occurring arsenic in parts of the state — odorless and tasteless, so only testing reveals it.
- Nitrate from agricultural and septic influence, especially in farmed areas.
- Naturally occurring uranium in some aquifers.
- Iron and manganese causing staining and metallic taste (aesthetic).
- Hard water from carbonate (limestone/dolomite) aquifers.
These are documented possibilities, not a reading of your well
Frequently asked questions
What should well owners in Montana test for?
A practical panel for Montana private wells includes Total coliform bacteria, Nitrate (as N), pH, Arsenic, Uranium, Iron, Manganese, Total hardness. Test bacteria and nitrate at least annually and use a state-certified laboratory; confirm local recommendations with your state health department and Montana State University Cooperative Extension.
Are private wells regulated in Montana?
Private wells are generally not covered by the federal Safe Drinking Water Act, though Montana or local rules may apply to construction, permitting, or testing. Public-system limits such as EPA MCLs are useful reference points, not automatic legal limits for your well.