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How often to test a private well
Every agency agrees on a yearly bacteria test. After that the schedules differ. Here they are side by side, with a source for each.
Every year
| Source | Yearly tests |
|---|---|
| CDC1 | Total coliform bacteria, nitrates, total dissolved solids, pH |
| Pennsylvania DEP2 | Total coliform bacteria, nitrates, total dissolved solids, pH |
| New Hampshire DES3 | Bacteria, nitrate, nitrite |
| Maine CDC4 | Coliform bacteria, E. coli, nitrates, nitrites |
| Michigan DHHS (via Livingston County)5 | Coliform bacteria, nitrate, nitrite |
| New Jersey (NJ Department of Health, via NJDEP)6 | Total coliform, nitrate, pH |
| Union County, NC7 | Coliform bacteria, including fecal coliform |
Every few years
| Source | Interval | Tests |
|---|---|---|
| New Hampshire DES3 | Every 3–5 years | Arsenic, chloride, copper, fluoride, hardness, iron, lead, manganese, pH, radon, sodium, uranium, PFAS (NHDES says it's acceptable to wait longer on PFAS if a first test found none and nearby land use hasn't changed) |
| Maine CDC4 | Every 3–5 years | Arsenic, chloride, copper, fluoride, hardness, iron, lead, magnesium, manganese, pH, radon, sodium, uranium |
| Michigan DHHS (via Livingston County)5 | Every 3–5 years | Arsenic, lead, copper |
| New Jersey6 | At least every 5 years | PFAS, lead, VOCs, SOCs, iron, manganese |
| Union County, NC7 | Every 2–3 years | Heavy metals, nitrate, nitrite, lead, copper |
| Union County, NC7 | Every 5 years | Pesticides and VOCs (yearly if a particular pesticide is applied in your area) |
At least once
- Minnesota recommends every well be tested for arsenic at least once.8
- New Jersey recommends arsenic, mercury, gross alpha and uranium at least once.6
- Maine recommends a comprehensive test of everything on its list if you've never tested.4
Events that call for a test
Maine CDC lists these as other times to test, and Livingston County, MI lists several as reasons for a bacteria test:45
- Buying a home with a well. NHDES and Maine CDC both say to test.34
- Pregnancy or a new baby. Maine CDC lists expecting a baby.4 Livingston County, MI suggests a bacteria test when someone becomes pregnant or an infant lives in the home.5
- A change in taste, smell or color, or cloudy water after rain.45
- Flooding over the top of the well.5
- Work on the well or water system, or a new or serviced treatment system.45
- The well runs dry and comes back.4
- Unexplained flu-like illness in the household, or a possible contamination source (septic, barnyard) within 50 feet.5
- After installing treatment, test the treated water, then every 3–5 years (NHDES).3
Where to get tested and treatment options
Related guides
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CDC, "Guidelines for Testing Well Water." https://www.cdc.gov/drinking-water/safety/guidelines-for-testing-well-water.html ↩
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Pennsylvania DEP, "Private Wells: Water Testing." https://www.pa.gov/agencies/dep/residents/my-water/private-wells/water-testing ↩
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NHDES, "Water Testing Guidance for Private Well Users" (April 2026). https://www.des.nh.gov/sites/g/files/ehbemt341/files/documents/labs-private-wells.pdf ↩↩↩↩
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Maine CDC, "Private Well Water." https://www.maine.gov/dhhs/mecdc/healthy-living/health-and-safety/drinking-water-safety/private-well-water ↩↩↩↩↩↩↩↩↩
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Livingston County, MI, Environmental Health, "Water Quality Testing for Wells" (MDHHS routine schedule). https://milivcounty.gov/environmental-health/wells/water-quality/ ↩↩↩↩↩↩↩↩
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NJDEP, "Private Wells: Well Testing." https://dep.nj.gov/privatewells/testing/ ↩↩↩
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Union County, NC, Environmental Health, "Wells and Water Testing." https://www.unioncountync.gov/government/departments-a-e/environmental-health/wells-and-water-testing ↩↩↩
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Minnesota Department of Health, "Arsenic in Drinking Water." https://www.health.state.mn.us/communities/environment/water/contaminants/arsenic.html ↩