Private well water testing

If your water comes from a private well, nobody tests it unless you do. Public water systems are monitored under federal rules; private wells are not, and most states have zero or limited regulations for them. EPA: Private Drinking Water Well Programs in Your State This page covers what to test for, how to get a reliable sample, and how to keep the results useful. [EPA-STATES source note]

What should you test well water for?

The CDC recommends testing well water at least once every year for total coliform bacteria, nitrates, total dissolved solids and pH. CDC: Guidelines for Testing Well Water EPA gives the same annual list. EPA: Protect Your Home's Water [CDC-TEST source note] [EPA-PROTECT source note]

Which local contaminants should you add?

Beyond the core panel, the CDC suggests asking your health or environmental department which other germs or chemicals matter in your area. Depending on location, that can include volatile organic compounds, lead, arsenic, mercury, radium, and pesticides or herbicides. CDC: Guidelines for Testing Well Water Guidance for home inspectors also mentions arsenic and radon as common local concerns. Water Systems Council: wellcare Guide to Evaluating Water Wells (for home inspectors) [CDC-TEST source note] [WSC-INSPECTOR source note]

What a well water test can't tell you

A test describes the water on the day it was sampled, for the contaminants on the panel. It says nothing about contaminants that weren't tested, and conditions change with seasons, floods, nearby land use and repairs. That is why the guidance stresses yearly testing plus event-driven tests rather than a single clean result.

Should you use a test kit or a certified lab?

Ask for a lab certified for drinking water analysis; the Minnesota Department of Health, for example, recommends an accredited laboratory. Minnesota Department of Health: Bacterial Safety of Well Water California's state guide notes that home test kits may not provide numerical concentrations, so lab analysis is often needed for specific results. California State Water Board: A Guide for Private Domestic Well Owners (2025) [MDH-BACTERIA source note] [CA-SWRCB-GUIDE source note]

How do you take a well water sample?

Follow the lab's instructions exactly; they differ by test. In general:

1. Use only the sterile bottles the lab provides, and don't touch the inside of the cap.
2. Sample from a cold-water tap that is used regularly, usually without an aerator or filter on it.
3. Note whether the sample passed through any treatment equipment.
4. Keep bacteria samples cold and deliver them within the lab's time limit.
5. Record the date, tap and any recent work on the well.

When should you test well water again?

Test again when something changes: flooding, nearby construction, repairs to the well system, a change in taste, color or smell, a pregnancy, or a child joining the household. Read how often to test well water for the full list.

What does well water testing cost?

Lab prices vary by state, lab and panel, so ask for an itemized quote. A basic bacteria test is usually the least expensive item; adding nitrate, metals such as arsenic or lead, radon or a broader chemical panel raises the price. Some county health departments and extension offices run or subsidize testing programs, so ask them first. The cheapest useful test is the core annual panel; the most expensive mistake is skipping it.

Testing when you buy or build

For a home purchase, test before closing and ask the seller for past results; see well inspection cost for how water testing fits with the rest of the evaluation. For a new well, the water should be tested after disinfection and before you drink it, and again after any repair to the system, which the CDC lists as a reason to test. CDC: Guidelines for Testing Well Water If a test comes back positive for bacteria, the test results guide walks through the next steps. [CDC-TEST source note]

What should you do with the results?

Store each report with your well log and maintenance records; NGWA's owner checklist recommends keeping construction reports, maintenance records and water test results somewhere safe. NGWA (Wellowner.org): Homeowner's Maintenance Checklist A run of results over years shows trends a single test can't. When the report arrives, use how to read well water test results to interpret it. [NGWA-CHECKLIST source note]