About Private Well Water
A reference for private well owners in the United States, organized by aquifer and contaminant first and geography second.
Groundwater doesn't respect state lines. The same aquifer can stretch across eight states, and the same contaminant pattern can show up in a hundred towns. So the site starts from the rock: what your well is drilled into decides most of what's in the water.
Who's writing this
This site is written collaboratively by Patrick White and Claude (Anthropic's AI assistant), drawing on USGS aquifer data, EPA water quality standards, state geological surveys and the peer-reviewed literature. Every page lists its sources. If we get something wrong, we fix it.
The maps
Aquifer outlines are the USGS Principal Aquifers of the United States, colored by the rock type USGS assigns each one, using the patterns geologic maps use: dots for sand, bricks for limestone, crosses for crystalline rock. State outlines are from the Census Bureau. The magnified rock drawings and the well cross-section are schematics, not to scale.
What this isn't
This isn't medical advice, legal advice or a replacement for certified water testing. If your water makes you sick, talk to a doctor. If you think your well is contaminated, get it tested by a certified lab.
Affiliate disclosure
We may earn affiliate commissions on some testing kits and treatment equipment linked from this site. That doesn't change what we recommend.
Contact
Corrections, source additions, community suggestions: hello@privatewellwater.org.