How to choose a certified lab for well water testing

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Your state certifies drinking water labs.

The EPA leaves lab certification to the states. Each state runs a program that checks labs and lists the ones certified to test drinking water. The EPA keeps a page with a link to every state's program.

The EPA's advice to private well owners is short: always use a state certified laboratory.

Check that the lab is certified for each test you want.

Certification is test by test. The Minnesota Department of Health warns that not every lab is certified for drinking water, and many are certified for only 1 or 2 tests. A lab certified for bacteria may not be certified for arsenic or PFAS.

Look the lab up on your state's list and confirm each test, or ask the lab to tell you in writing.

Ask these questions before you order.

• Which tests are you certified for? Get the list.
• What are your reporting limits? The reporting limit is the smallest amount the lab can measure. It needs to be lower than the health limit, or a "not detected" result won't tell you much. Penn State's example lab report shows arsenic as "less than 0.003 mg/L," well under the EPA's 0.010 mg/L limit.
• Do you send bottles and instructions? You'll need the lab's own sample bottles.
• When do bacteria samples have to arrive? Bacteria tests have a short window. Wisconsin's limit is 30 hours from when you fill the bottle to when the lab starts the test, so ask which days the lab accepts them.
• Do you explain results? Some labs flag results that are over the limit. Ask what they include.

Start with your health department.

Your county or state health department may test well water itself, or it can point you to certified labs nearby. The CDC suggests asking your health department which contaminants to test for where you live. That way you don't pay for tests you don't need.

Be careful with in-home tests from salespeople.

Penn State Extension says not to rely on in-home water tests run by people selling treatment equipment. Get results from a certified lab before you buy a filter or softener.

Follow the lab's sampling steps exactly.

Use only the bottles the lab sends, and follow its written instructions step by step. Get the sample back to the lab within the time it gives you.

When the report comes back, our guide to reading a well water test explains the units and what to do next.

Questions people ask