Colorado Well Water
Last reviewed October 29, 2026
Overview
Private wells supply water to many Colorado 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
Colorado’s wells tap alluvial valley aquifers and bedrock aquifers such as the Denver Basin. The documented regional concerns below indicate what is worth testing for — not what any individual well contains.
Documented regional concerns
- Naturally occurring uranium in some aquifers.
- Naturally occurring radium/radionuclides in some deep aquifers.
- Nitrate from agricultural and septic influence, especially in farmed areas.
- Naturally occurring selenium in some western aquifers.
- 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 Colorado test for?
A practical panel for Colorado private wells includes Total coliform bacteria, Nitrate (as N), pH, Uranium, Radium / gross alpha, Selenium, Total hardness. Test bacteria and nitrate at least annually and use a state-certified laboratory; confirm local recommendations with your state health department and Colorado State University Cooperative Extension.
Are private wells regulated in Colorado?
Private wells are generally not covered by the federal Safe Drinking Water Act, though Colorado 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.