Well Water Notebook
Information only, not medical advice. We never say whether your water is safe to drink. Ask a state-certified lab or your local health department. Disclaimer

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Nitrate in well water: testing, infants, and treatment options

Nitrate is one of the few things every agency says to test for every year. Bottle-fed babies are the most at risk. Here's what the 10 mg/L number means, which wells are most vulnerable, and what agencies say to do, with a source for every claim.

This guide can't tell you whether your water is safe to drink. If a baby in your home drinks formula made with well water and you have a nitrate result, talk to your doctor and health department now.

The number

EPA's drinking water standard for nitrate is 10 mg/L measured as nitrogen (1 mg/L is the same as 1 part per million). Minnesota's health department says that, based on current data, this standard protects infants against methemoglobinemia, and that infants are the most sensitive group for known health effects.1

Why babies are the concern

Too much nitrate affects how blood carries oxygen and can cause methemoglobinemia ("blue baby syndrome"). Bottle-fed babies under six months are at the highest risk. It can cause serious illness or death, can turn lips and skin bluish, and may be hard to spot in infants.1

Don't boil it. Minnesota says boiled water isn't a safe option, because boiling makes nitrate more concentrated.1

Which wells are most at risk

Minnesota lists these as the most vulnerable to nitrate, especially older wells (built before 1974), wells near septic systems, and wells in agricultural areas:1

Local data can be striking. In Penn State's lab summary for Lancaster County, PA, 24.8% of 403 samples were over 10 mg/L.2 See the Lancaster County page.

Testing

If your nitrate is high

Minnesota's steps:1

  1. Use a safe alternative source such as bottled water until the problem is fixed. This matters most if babies under six months drink formula made with the water.
  2. Have a licensed well contractor inspect the well for damage.
  3. Find and remove sources of nitrate on your property.
  4. Consider home water treatment, after you've worked on the sources.

Treatment types

Maine CDC's treatment chart lists reverse osmosis and anion exchange for nitrate/nitrite.8 Reverse osmosis wastes about 2–4 gallons for each gallon treated. Anion exchange resin has to be regenerated or flushed regularly.8 Choose a unit certified for nitrate reduction where certification exists (NSF, UL or WQA), as Minnesota recommends for any treatment.9

Where to get tested and treatment options

Testing: any state-certified lab, your state lab, or your health department. See your county page and best way to test well water.

Treatment: point-of-use reverse osmosis or anion exchange, as listed above. See whole-house vs. point-of-use.

  1. Minnesota Department of Health, "Nitrate in Drinking Water." https://www.health.state.mn.us/communities/environment/water/contaminants/nitrate.html ↩↩↩↩↩

  2. Penn State Agricultural Analytical Services Laboratory, "Summary of Drinking Water Samples Tested: Lancaster County." https://agsci.psu.edu/aasl/water-testing/drinking-water-testing/drinking-water-test-summaries/lancaster ↩

  3. CDC, "Guidelines for Testing Well Water." https://www.cdc.gov/drinking-water/safety/guidelines-for-testing-well-water.html ↩

  4. Pennsylvania DEP, "Private Wells: Water Testing." https://www.pa.gov/agencies/dep/residents/my-water/private-wells/water-testing ↩

  5. Maine CDC, "Private Well Water." https://www.maine.gov/dhhs/mecdc/healthy-living/health-and-safety/drinking-water-safety/private-well-water ↩↩

  6. 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 ↩

  7. Livingston County, MI, Environmental Health, "Water Quality Testing for Wells" (MDHHS schedule). https://milivcounty.gov/environmental-health/wells/water-quality/ ↩↩

  8. Maine CDC, "Quick Guide to Well Water Treatment" (PDF). https://www.maine.gov/dhhs/mecdc/sites/maine.gov.dhhs.mecdc/files/Well-water-treatment8.27.2026.pdf ↩↩

  9. Minnesota Department of Health, "Home Water Treatment Facts." https://www.health.state.mn.us/communities/environment/water/factsheet/hometreatment.html ↩