Water · Water Treatment
Test for agricultural runoff in well water. The EPA limit is 10 mg/L. Especially important if your household includes infants under six months.
The basics
Nitrate is a nitrogen compound that enters groundwater primarily through agricultural fertilizer, animal waste, and septic system leaching. It is colorless, odorless, and tasteless, which means you cannot detect it without testing. The EPA has set the maximum contaminant level (MCL) for nitrate at 10 mg/L (measured as nitrogen) in drinking water. The MCL for nitrite is 1 mg/L.
The primary health concern is methemoglobinemia, sometimes called blue baby syndrome. Infants under six months are most vulnerable because their digestive systems convert nitrate into nitrite, which interferes with the blood's ability to carry oxygen. Water above 10 mg/L should not be used to prepare infant formula. Adults generally tolerate low levels without acute symptoms, but long-term exposure at elevated levels is an area of ongoing research.
Safety notice
Source: EPA National Primary Drinking Water Regulations. Verified June 14, 2026.
If your household uses a private well, especially in an agricultural area, annual nitrate testing is a minimum. Test more frequently if you have infants, are pregnant, or live near cropland, feedlots, or septic systems. Test again after heavy rains or flooding, which can spike nitrate levels in shallow wells. Municipal water systems are required to test and report nitrate levels, so public water users generally do not need to test at home unless they have specific concerns.
One pack is enough for annual testing plus a few extra strips for post-storm or post-flood checks. At $10 to $20 per pack, they are inexpensive insurance for well water households. If a strip indicates elevated nitrate, follow up with a certified lab test for a precise concentration reading.
Store in the original sealed container, cool and dry, away from direct sunlight. Humidity degrades the test pads and can cause inaccurate readings. Most packs carry a two-year shelf life when stored properly. Replace if the strips show discoloration before use or if the expiration date has passed.
Brand does not matter. Look for test strips that are calibrated to detect nitrate at or near the 10 mg/L EPA MCL. Most strips sold for drinking water testing meet this threshold. Pool supply test strips may use different scales, so confirm the measurement range before purchasing.
Where to buy
Search for nitrate/nitrite test strips rated for drinking water. Verify the strip measures at or near the 10 mg/L EPA MCL before purchasing. Pool supply strips may not be calibrated for drinking water ranges.
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