Well Water Testing Guide
What to test for, how to find a certified lab, how often to test, and what to do with results.
If your home uses a private well, you are responsible for testing and treating your own water. The EPA does not regulate private wells - there are no federal requirements for testing or treatment. That makes regular testing essential, because contamination can occur without any change in taste, color, or odor.
Why Test?
Well water quality can change over time due to seasonal variations, nearby land use changes (agriculture, construction, septic systems), natural geological conditions, or problems with the well casing or cap. The CDC estimates that approximately 23 million U.S. households rely on private wells, and contamination issues are more common than many homeowners realize.
What to Test For
The EPA recommends the following minimum tests for private wells:
Annual Tests (Every Year)
- Total coliform bacteria and E. coli - indicates possible contamination from sewage or animal waste
- Nitrate - common from agricultural runoff and septic systems; particularly dangerous for infants
- pH and total dissolved solids (TDS) - general water quality indicators
Every 3–5 Years (or as Needed)
- Lead and copper - from plumbing and well components
- Arsenic - naturally occurring in many aquifers
- Iron and manganese - common nuisance contaminants
- Hardness - calcium and magnesium content
- Sulfate and chloride - taste and corrosion indicators
Situational Tests
- PFAS - if near industrial sites, military bases, or airports
- Radon - in areas with known radon in soil
- Pesticides/herbicides - near agricultural land
- Volatile organic compounds (VOCs) - near gas stations, dry cleaners, or industrial sites
- Uranium and radium - in areas with known geological deposits
How to Find a Certified Lab
Use a state-certified drinking water laboratory for accurate results. Here is how to find one:
- Contact your state's department of health or environmental quality. Most maintain a list of certified labs on their website.
- Check the EPA's Safe Drinking Water Information System for contacts.
- Your local cooperative extension office can often recommend labs and may offer discounted testing.
- Cost: A basic bacteria and nitrate test runs $25–$75. A comprehensive panel (metals, minerals, VOCs) runs $100–$300. PFAS testing costs $200–$400.
How Often to Test
| Test | Frequency |
|---|---|
| Bacteria (coliform, E. coli) | Annually, and after any well repair |
| Nitrate | Annually |
| Lead, arsenic, metals | Every 3–5 years |
| PFAS | At least once; repeat if near known source |
| Full panel | When you buy or move into a home with a well |
Also test whenever you notice a change in taste, color, or odor; after flooding or nearby construction; after well repairs; or if someone in the household becomes ill with gastrointestinal symptoms.
What to Do With Results
Compare your results to EPA maximum contaminant levels (MCLs). If any contaminant exceeds the MCL or health advisory level, treatment is recommended. Our Well Water Treatment Planner can help you build a multi-stage treatment chain based on the specific contaminants found in your test results. You can also look up individual contaminants in our Contaminants Guide to understand health effects and removal methods.
Sources
Educational guidance only - consult your water utility or a certified lab for situation-specific recommendations.