Last checked: October 22, 2026

Private well testing checklist

A printable checklist of when to test a private well, what to ask the lab for, and how to take a sample. It draws on CDC and state health and environment agencies, and every item links to its source.

Download the printable PDF Free, no sign-up. 3 pages, US Letter.

1. Every year

• Total coliform bacteria, nitrates, total dissolved solids and pH. This is CDC's yearly list.¹ Pennsylvania DEP recommends the same four.²
• Anything else your state adds. For example, New Hampshire adds nitrite,³ Maine CDC lists coliform bacteria, E. coli, nitrates and nitrites,⁴ and New Jersey lists total coliform, nitrate and pH.⁵
• A spring check of the well itself. CDC says to check your well every spring, at a minimum, to make sure there are no mechanical problems.¹

2. Every few years, and at least once

• Every 3–5 years (New Hampshire): arsenic, chloride, copper, fluoride, hardness, iron, lead, manganese, pH, radon, sodium, uranium and PFAS.³
• Every 3–5 years (Maine): arsenic, chloride, copper, fluoride, hardness, iron, lead, magnesium, manganese, pH, radon, sodium and uranium.⁴
• At least every 5 years (New Jersey): PFAS, lead, VOCs, SOCs, iron and manganese.⁵
• At least once: Minnesota recommends testing every well for arsenic at least once.⁷ New Jersey recommends arsenic, mercury, gross alpha and uranium at least once.⁵
• Never tested? Maine CDC recommends a comprehensive test of everything on its list.⁴

Schedules differ by state. See how often to test a private well for a side-by-side table.

3. After floods, repairs and other events

CDC says to have your well water tested if:¹

• You're told there are problems with well water in your area
• There are problems near your well, such as flooding, land disturbances, or nearby waste disposal sites
• You replace or repair any part of your well system
• You notice a change in your water's taste, color or smell
• You or someone you live with becomes pregnant
• A child starts living with you

Maine CDC adds: when the well runs dry and comes back, and after a new or serviced treatment system.⁴ After installing treatment, NHDES says to test the treated water.³ If a well needs disinfecting, see shock chlorinating a well, and retest afterward as your health department advises.

4. When buying a home with a well

For the full process (contingencies, flow tests, septic distances, red flags and each state's home-sale rule), see Buying a home with a well.

• Test before you buy. NHDES and Maine CDC both recommend testing when buying a home with a well.³⁴
• Check your state's rules. In New Jersey, the Private Well Testing Act requires testing when a property with a potable well is sold, and buyer and seller must both review the results before closing. Total coliform results are valid for only six months.⁶
• Ask for the full state panel, not just bacteria. Maine's state lab offers a "Residential Sales" kit.⁸
• Know what's being tested. If the house has treatment, NHDES notes buyers can test after treatment to check the treated water.³

5. By common local concern

Ask your health department what's common where you live. CDC says the right tests depend on where the well is, your state or region, and whether the area is rural or urban.¹

Our county pages list local data and contacts for each county we cover.

6. Sampling tips

• Get bottles from the lab and follow its instructions. Bacteria samples have to reach the lab within a holding time, so Maine CDC recommends checking that a lab can receive them in time from your area.¹¹
• For bacteria: remove the aerator if you can, disinfect the faucet tip, run cold water for 15–20 minutes, fill the bottle without touching the inside or the lid (leave any pill or powder in it), and keep it chilled until it reaches the lab. These are Livingston County, MI's instructions.¹⁰
• For lead and copper: take stagnant and flushed samples.³
• Treated or untreated? Decide which water you're testing, and tell the lab.³
• Check accreditation test by test. Maine CDC says labs are accredited for specific tests, so ask the lab exactly what it's accredited for.¹¹

7. Where to find a state-certified lab

CDC says to use a state-certified laboratory, and that your health department or county government should have a list.¹

• Any state: EPA keeps contact information for each state's lab certification program.
• New Hampshire: NHELAP Accredited Laboratory Search.³
• Maine: Maine CDC's list of in-state commercial drinking water labs.¹¹
• Pennsylvania: DEP's lists of accredited labs, linked from its water testing page.²
• New Jersey: NJDEP's certified laboratory search.⁶
• Michigan: EGLE's private well testing page lists health departments with onsite testing and the EGLE Laboratory.¹²
• North Carolina (Union County): Union County Environmental Health offers well sampling and testing.¹³
• Not sure what to test for? CDC lists the EPA Safe Drinking Water Hotline: (800) 426-4791.¹

8. After you get results

• Compare each result with the standard printed on the report. See how to read your well water test results.
• Call your local health or environmental department. CDC says they can help you understand the results and what to do next, and if results show harmful germs or chemicals, to consider bottled water or another safe source in the meantime.¹
• Keep every report, with the date and lab name, so you can compare over time.