Well water testing

If you have a private well, test it at least once a year for total coliform bacteria, nitrate, total dissolved solids and pH, using a state-certified laboratory (CDC). Add tests for anything your local health department flags, because the public water data that EPA publishes, and that this site uses, does not cover private wells.

Private wells are not regulated by the federal government under the Safe Drinking Water Act, or by most states (EPA). CDC says the well owner is responsible for testing (CDC).

What public water data does not cover

A public water system has at least 15 service connections or serves an average of at least 25 people for at least 60 days a year (EPA). The data people usually rely on is about those systems, so none of it describes your well:

• Water quality reports (CCRs). Households on private wells do not get one (CDC).
• UCMR 5. EPA's 2023 to 2025 survey of 29 PFAS and lithium sampled public water systems (EPA).
• EPA's PFAS limits. They apply to public water systems (EPA).
• This site's water system pages. They are built from that same public-system data (methodology).

About 15% of the US population, over 43 million people, rely on private wells. A USGS study of 2,100 private wells found that about one in five had at least one contaminant above a human-health benchmark (EPA).

Nearby data can still give clues. EPA suggests asking your health department, or nearby utilities that use groundwater, about contaminants of concern in your area (EPA). But only testing your own well confirms what is in it (USGS).

The yearly test

When to test for more

EPA matches extra tests to what is near your well and what you notice at the tap (EPA):

• Plumbing or service lines that contain lead: pH, lead and copper.
• Intensive farming nearby: nitrate, nitrite, pesticides and coliform bacteria.
• Gas drilling nearby: chloride, sodium, barium and strontium.
• A landfill, gas station or dry cleaner nearby: volatile organic compounds, total dissolved solids, pH, sulfate, chloride and metals.
• Scale, or soap that won't lather: hardness. Enter the result in our softener size calculator.
• Stained fixtures or laundry: iron, copper and manganese.

CDC also says to test after flooding or land disturbance near the well, after any well repair, when the water's taste, color or smell changes, when someone in the home becomes pregnant, and when a child comes to live with you (CDC).

Two contaminants worth asking your health department about:

• Lithium, which can be higher in groundwater in arid parts of the West (EPA). See lithium in tap water.
• PFAS. A USGS tap water study found PFAS concentrations were similar in private wells and public supplies (USGS). See PFOA and PFOS limits explained.

Where to test

Use a state-certified laboratory (CDC). EPA does not test home water on request, but it links to each state's laboratory certification program (EPA). Your local health department may test private wells for free (EPA). A home TDS meter is no substitute; see TDS meters: what they can't tell you.

When results come back

Your lab report should list the concentration of each substance tested, and it may compare them with EPA's standards (EPA). If something is above a health standard, EPA says to contact your health department and have the well retested to confirm (same source). If the results show harmful germs or chemicals, CDC suggests considering bottled water or another safe source of water, and your health department can help with next steps (CDC).

If your home has lead plumbing, see lead pipes and lead filters for EPA's advice on filters certified to reduce lead.