Short version: CDC recommends testing private well water at least once a year for total coliform bacteria, nitrates, total dissolved solids (TDS), and pH. For other contaminants, ask your local health department which tests are relevant where you live. Use a state-certified laboratory and follow its sample-collection instructions. Lab prices depend on the tests and sampling service; see our well-water testing cost guide for current official fee examples.
What should a routine test include?
CDC lists four baseline measures for annual testing:
- Total coliform bacteria, which can indicate that germs may be present.
- Nitrates, which can enter groundwater from several sources and can be especially harmful to infants at high levels.
- Total dissolved solids (TDS), a measure of dissolved substances in water.
- pH, which indicates how acidic or basic the water is.
This is a starting point, not a complete panel for every property. Local geology, nearby land uses, flooding, and well construction can change which additional tests are appropriate.
When should I test sooner?
CDC advises testing if there are known local well-water problems, flooding or other nearby disturbances, a repair to part of the well system, a change in the water’s taste, color, or smell, or a new pregnancy or child in the household. Contact your health department if you suspect a particular contaminant; it can help identify the right test rather than paying for an unfocused panel.
How do I find a lab?
- Contact your state or local health department or environmental department and ask for the list of state-certified drinking-water laboratories.
- Confirm the lab is certified for the specific contaminants you want to test.
- Use the lab’s bottles and follow its exact collection, storage, and delivery instructions. Improper collection can affect results.
- Ask the lab how results are reported and whom to contact if a result is outside a guideline or standard.
Start with the step-by-step guide to finding a certified water testing lab. Michigan residents can also use our Michigan well-water testing pilot for EGLE’s homeowner lab process and current state fee examples. Do not rely on appearance, taste, or odor to confirm water safety. Some contaminants cannot be detected by sight, smell, or taste.
What should I do with results?
Ask the laboratory or local health department to explain the results and applicable local guidance. Our guide to reading a well water test report covers common report fields and questions to ask. For a nitrate result, first check whether the lab reported it as nitrogen or nitrate; see our nitrate units and next-steps guide. If a contaminant is identified, choose treatment based on that measured issue and verify that a system is independently certified for the exact reduction claim. A general “whole house” or “purifying” label does not tell you which substances a unit has been tested to reduce.
Primary sources
- CDC: Guidelines for Testing Well Water — annual baseline tests, circumstances for testing, and finding a state-certified lab.
- U.S. EPA: Protect Your Home’s Water — well testing and local contaminant considerations.
- U.S. EPA: Home Drinking Water Filtration Fact Sheet — choosing treatment based on a specific concern.
This page provides general educational information. It does not interpret individual test results, diagnose a health risk, or recommend a particular treatment for your home. Follow your lab and local public-health department’s advice.