How often to test well water: routine tests and event checks
General information, not medical advice. This page explains what the EPA, CDC and state health departments say. It cannot tell you whether your water is safe. For that, ask your certified lab or local health department. Read the full disclaimer.
The CDC's answer to how often to test well water is at least once every year for total coliforms (types of bacteria), nitrates (chemicals), total dissolved solids (how much material is mixed into the water) and pH (how acidic or basic it is). It also calls for testing when certain events happen, including flooding near the well, well-system repairs and a change in the water's taste, color or smell.
Ask your state or local health department which other tests matter where you live, and use a state-certified laboratory. The CDC recommends both.
Standards, local geology and state requirements all vary. Confirm anything on this page with your state or local health department before acting on it.
Well water testing frequency: a routine date and event triggers
| Reason | What the CDC says |
|---|---|
| Routine testing | At least once every year: total coliform bacteria, nitrates, total dissolved solids and pH. Its annual list also includes other germs and chemicals of concern in your area. Ask your health department which apply. |
| Problems in the area or near your well | Also test if you are notified of local well-water problems, or if there are problems near your well such as flooding, land disturbances or nearby waste disposal sites. |
| Changes to the system, water or household | Also test if you replace or repair any part of your well system; notice a change in taste, color or smell; you or someone you live with becomes pregnant; or a child starts living with you. |
Table source: CDC, Guidelines for Testing Well Water, “What to test for” and “When to have your well tested.” Checked October 7, 2026.
The same CDC page says that if you think the well is contaminated with other harmful germs or chemicals, test for those too. It directs readers to start by asking their health department about local concerns. The event list gives reasons to test, not a new universal interval measured from the last sample.
How often should well water be tested for each item?
The EPA's Home Water Testing fact sheet also says to test every year for total coliform bacteria, nitrates, total dissolved solids and pH, “especially if you have a new well, or have replaced or repaired pipes, pumps or the well casing.” That is the EPA's wording, not a repair instruction.
State guidance can name additional tests and their frequency. For example, the Minnesota Department of Health's well-testing table says to test for coliform bacteria and nitrate every year, and for arsenic and lead at least once. Those entries are Minnesota guidance for the named tests, not a nationwide schedule for every contaminant. Ask your own health department which tests and repeat dates apply.
Do not confuse the spring well check with the water test
The CDC says: “At a minimum, check your well every spring to make sure there are no mechanical problems.” Its next sentence calls for testing the water at least once each year for the listed tests.
A mechanical check and a water test are different tasks in that passage. The spring wording belongs to the mechanical check. It does not set a spring-only date for the entire annual water-test list. Ask your lab or health department about timing for your tests rather than turning that sentence into an extra sampling rule.
Take the report and the reason for testing to your lab
The CDC's advice after testing includes this warning:
“If your test results show that there are harmful germs or chemicals in your well water, consider drinking bottled water or another safe source of water.”
It then says to contact your local health or environmental department, which can help explain the results and may recommend more frequent testing. Tell them the exact test name and result, and which change or event prompted the test.
If the report itself is hard to read, see the explanation of report units and symbols. A bacteria result has its own guide to total coliform and E. coli wording; a nitrate result may need its “as N” reporting basis checked. None of those pages decides whether a household should use its water.
Federal standards do not make this a private-well legal schedule
The CDC explains that the EPA's rules for public drinking-water systems do not apply to privately owned wells. The EPA's private-well page says private-well water is not regulated by the federal government under the Safe Drinking Water Act, nor by most state governments and laws. It also says private well owners are responsible for delivering safe drinking water to their households. Your state or local health department is the contact for the requirements where you live.
Sources and limits: This reference compiles the saved CDC, EPA and Minnesota Department of Health sources below. WellTestAdvisor has not tested water or products. It organizes the authorities' testing guidance, not a diagnosis or a household water-use decision.
Sources and check dates
- CDC, Guidelines for Testing Well Water. Annual tests, event list, spring check, test descriptions, warning and contact guidance. Checked October 7, 2026.
- EPA, Home Water Testing, May 2005 fact sheet, page 2. Annual-test wording and its new-well/repair qualification only. Still linked from the EPA's Home Drinking Water Testing page when checked October 7, 2026.
- Minnesota Department of Health, Well Testing, Results, and Options, “What to test your well water for.” Minnesota test-frequency entries only, not its treatment instructions. Checked October 7, 2026.
- EPA, Private Drinking Water Wells. Federal scope and private-well owner responsibility. Checked October 7, 2026.