How to read a well water test report

Start here: confirm the report is for the right sample, read each result with its unit and any comparison value shown, and ask the laboratory to explain unfamiliar flags or abbreviations. Private wells are not covered by the federal rules that apply to public water systems. For health meaning and next steps, contact your local health or environmental department.

1. Confirm which water sample the report describes

Check the sample ID, collection and receipt dates, sample location, and whether the sample was collected by you, the laboratory, or another person. A kitchen tap sample taken before treatment may answer a different question from a sample collected after a filter or softener. If the location or treatment status is missing or wrong, ask the lab before interpreting the results.

2. Match each result to the test you ordered

The report should identify the analyte or measurement the laboratory tested. A report only tells you about the substances included in that sample order; it does not screen for every possible contaminant. Compare the report against your order confirmation and ask whether a test was omitted, inconclusive, or reported separately.

3. Read the value together with its unit

Results may use different units depending on the test. Do not compare two numbers until you know they use the same unit and refer to the same analyte. Some laboratory reports also include detection or reporting limits and result qualifiers. Ask the lab what “not detected,” a less-than sign, or any letter code means on that specific report; these terms can depend on the method and reporting limit.

4. Understand what a comparison value does—and does not—tell you

A report may show a standard, guideline, or reference value next to a result. Ask who issued that value, what it applies to, and whether it is health-based, aesthetic, or a regulatory limit for public water systems. EPA drinking-water requirements apply to public water systems; they do not regulate private household wells. State and local recommendations for private wells can differ, so do not treat a public-system comparison as a private-well diagnosis or legal determination.

5. Ask the laboratory and local health department

• Was the sample collected and handled correctly for this test?
• What is the unit, method, detection limit, and meaning of any flag?
• Is the comparison value shown on the report applicable to a private well in my location?
• Should I collect a confirmation sample or test for anything else?
• Who can explain health-related implications and locally appropriate next steps?

CDC advises private-well owners to contact their health department for help understanding results and deciding what to do next. If a result indicates a possible health concern, follow that agency’s instructions about drinking water and any follow-up testing.

6. Keep reports together over time

Save the complete report, lab name, sample location, collection date, and any treatment or maintenance changes. A record helps you and local professionals compare like-for-like samples over time. If the source or sampling point changes, note that too.

For nitrate reports specifically, compare like units before comparing values. Our nitrate guide explains NO₃-N versus NO₃ and includes a unit converter.

Choose treatment only after the result is understood

If treatment is recommended, match it to the specific measured issue and verify the exact product model’s independently certified reduction claim. Confirm maintenance and retesting requirements. Do not choose a system from a broad “whole house” or “purifying” claim alone.

This educational guide cannot interpret your individual report, diagnose a health risk, or recommend a treatment system for your home. Use the laboratory and your state or local health department for case-specific interpretation.