Nitrate in well water: what the number means in New York

As of 2026-10-07. Limits come from US EPA and the New York State Department of Health (NYSDOH). Rules change; sources are linked below. Private wells aren't regulated like public water: NYSDOH uses public-water standards as guidelines for private wells.
Nitrate over 10 mg/L? NYSDOH says to stop using your well water and use bottled water for drinking, preparing food, or making ice if tests show contaminants, and to contact your local health department (find yours at health.ny.gov/contact/contact_information/). Don't boil it: the Minnesota Department of Health warns that boiling makes nitrate more concentrated. That's especially important if a baby under six months drinks formula made with the water.

The limit

TestNew York (NYSDOH)US EPA (public water)
Nitrate10 mg/L as nitrogen (N)10 mg/L as N
Nitrite1 mg/L as N1 mg/L as N

The limits are written "as N" (as nitrogen). Check that your report uses the same units; if it doesn't say, ask your lab. NYSDOH's private-well fact sheet uses these public-water numbers as its recommended limits.

Why it matters

EPA: "Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome." EPA's private-well page adds that high nitrate/nitrite reduces the blood's ability to carry oxygen, and that this acute condition "can occur rapidly over a period of days." NYSDOH lists nitrate and nitrite as "most harmful to babies."

Where it comes from

EPA lists chemical fertilizers, human sewage, and animal waste and fertilizers as sources, reaching wells through groundwater movement, surface-water seepage, and runoff. EPA's drinking water table also lists leaking from septic tanks and sewage, and erosion of natural deposits. NYSDOH suggests testing for nitrate, pesticides, arsenic, and coliform bacteria if you're near intensive agriculture. Its Private Well Risk Mapper shows agricultural-runoff risk for an address.

How often to test

NYSDOH recommends testing for nitrate and nitrite every 3–5 years, plus bacteria every year. It also suggests extra testing when your household changes, for example a pregnancy or a new baby. EPA's general advice is to test private wells for nitrates every year. Use a NYSDOH ELAP-certified lab: NYSDOH recommends not relying on in-home tests by water treatment vendors or store-bought kits, because they don't meet ELAP standards.

If your result is high

Where NYSDOH doesn't address a point, we cite the Minnesota Department of Health; your local health department's advice comes first.

  1. Switch to bottled water for drinking, preparing food, and making ice, and call your local health department (NYSDOH). The Minnesota Department of Health stresses this for babies under six months who drink formula made with the water.
  2. Have the well re-tested to confirm the result (EPA).
  3. Look for and remove likely sources near the well: fertilizer, manure, or septic problems. NYSDOH recommends storing pesticides, fertilizers, manure, and similar substances at least 100 feet from the well casing.
  4. Ask a well contractor to check the well itself for damage (Minnesota Department of Health).
  5. Ask about treatment. The Minnesota Department of Health lists anion exchange, distillation, and reverse osmosis as types that can reduce nitrate. It also recommends that babies under six months not drink the treated water, in case the treatment stops working.

The NY guide covers nitrate along with about two dozen other tests, with an urgency triage and a fill-in worksheet. Already have results with several numbers? Start with reading your results, or see coliform and PFAS.

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Sources