Well Water
Private Well Water Guide
Over 43 million Americans rely on private wells. Unlike public water systems, private wells are not federally regulated — testing, treatment, and maintenance are entirely the homeowner's responsibility.
Private wells have no mandatory testing requirements. The EPA recommends annual testing at minimum.
Why This Matters
Public water systems serving 25 or more people are regulated under the Safe Drinking Water Act and must test water regularly, report results to the public, and fix violations. Private wells serving fewer than 25 people have none of these requirements. Contamination that would trigger a public health notice for a utility can go undetected in a private well for years.
How to Approach Well Water Testing
Test annually at minimum
Coliform bacteria and nitrates should be tested every year regardless of state. Most certified labs offer a basic well panel for $75–$200.
Know your local risks
Your state geology, nearby agriculture, and industrial history determine which additional tests matter. Select your state below for a specific risk profile.
Use a certified lab
Standard home test kits are unreliable for health-based contaminants. Use a state-certified or NELAP-accredited laboratory for results you can act on.
Retest after any change
Heavy rain events, nearby construction, flooding, changes in taste/odor/color, or new neighbors with septic systems are all triggers for retesting.
What to Test For — Common Well Water Contaminants
The right tests depend on your location, nearby land use, and well age. These are the most commonly detected or risk-relevant contaminants across U.S. private wells.
Coliform Bacteria
Universal risk — always test annually
Nitrates
Agricultural areas especially — infant risk
Arsenic
Southwest, West — naturally occurring
Lead
Old well casings, pre-1986 household plumbing
PFAS
Near military bases, airports, industrial sites
Radon
Granite geology, Northeast, Southeast
Hardness
Equipment and plumbing — not a health hazard
Iron & Manganese
Taste, staining — aesthetic concern
State-Specific Well Water Guides
Contaminant risks, testing requirements, and lab referral programs vary by state. Select your state for location-specific guidance.
California Well Water Guide
Approximately 10% of Californians — over 4 million people — rely on private wells for drinking water. California's diverse geology creates region-specific contamination risks: naturally occurring arsenic and uranium in the Central Valley and foothills, nitrate contamination from intensive agriculture, PFAS near military installations, and hexavalent chromium (chromium-6) in several inland regions. The State Water Resources Control Board oversees small water systems, but private domestic wells are the responsibility of the homeowner.
Key risks:
Texas Well Water Guide
Texas has approximately 1.5 million private water wells, with rural and suburban residents across the Hill Country, West Texas, and the Panhandle commonly relying on groundwater. The state's primary well water concerns include naturally occurring arsenic (particularly in West Texas and the Hill Country), high nitrates from agricultural and septic sources, radium and uranium in granite-dominated regions, and bacterial contamination in shallow alluvial wells. The Texas Commission on Environmental Quality (TCEQ) oversees public water systems; private wells are the landowner's responsibility.
Key risks:
Florida Well Water Guide
Florida has over 1 million private wells, with use concentrated in rural areas of North and Central Florida. Florida's unique geology — primarily porous karst limestone (the Floridan Aquifer System) — creates both the state's water abundance and its contamination vulnerabilities. Key concerns include naturally occurring radium, uranium, and radon from phosphate-rich limestone, nitrate and bacterial contamination from septic systems and agricultural runoff, and legacy contamination from the phosphate mining industry in the central state.
Key risks:
Arizona Well Water Guide
Arizona's private well users — primarily in rural areas outside the Phoenix and Tucson metro served areas — face some of the most challenging well water conditions in the nation. The state's arid geology concentrates naturally occurring contaminants including arsenic, uranium, fluoride, and chromium-6 in groundwater. Aquifer overdraft is also a serious concern, with many rural Arizona wells experiencing declining water levels. The Arizona Department of Environmental Quality (ADEQ) regulates public water systems; private domestic wells (fewer than 5 service connections) are minimally regulated.
Key risks:
Ohio Well Water Guide
Ohio has over 800,000 private wells serving approximately 2 million residents, concentrated in rural areas outside municipal water service areas. Ohio's glacial geology, agricultural intensity, and legacy industrial history create a complex contamination landscape. Primary concerns include nitrate from agriculture and septic systems, bacteria from karst geology in northwest Ohio and the limestone belt, lead from older well pump and pressure tank components, and PFAS from industrial sources concentrated in the northeastern and central portions of the state.
Key risks:
Well water guides for additional states will be added as coverage expands in Phase 2.
Official EPA Well Water Resources
The EPA's Private Wells program is the authoritative federal resource for well owners. It includes guidance on testing, treatment, and finding certified labs.
EPA Private Wells Program