Nitrate and nitrite are nitrogen compounds that can get into drinking water from fertilizer, animal waste, septic systems, wastewater, and natural sources. They are especially important for private wells because you cannot see, taste, smell, or measure them with a TDS meter.
Quick answer
- EPA's primary standard for nitrate as nitrogen is 10 mg/L.
- EPA's primary standard for nitrite as nitrogen is 1 mg/L.
- Private wells near farms, septic systems, feedlots, or disturbed land should take nitrate testing seriously.
- Infants are a key risk group in official guidance.
- Use a lab or local health department when nitrate results affect drinking decisions.
Safety note: Clear water and low TDS do not prove safety and do not rule out nitrate. Do not use taste, smell, pH, or a generic filter label as proof that nitrate is not present.
What nitrate is
Nitrate and nitrite are forms of nitrogen. In drinking-water discussions, nitrate often matters because it can move through soil into groundwater. It is a common private-well concern in agricultural areas, but agriculture is not the only possible source. Septic systems, animal waste, fertilizer, wastewater, and natural deposits can also matter.
EPA's potential well-water contaminants page lists nitrate as a contaminant that can come from fertilizer, sewage, and erosion of natural deposits. EPA also notes infant-health concerns, including methemoglobinemia, often called blue-baby syndrome.
For the bigger testing path, start with How To Test Drinking Water at Home.
EPA nitrate and nitrite limits
EPA's national primary drinking-water regulations list nitrate as nitrogen at 10 mg/L and nitrite as nitrogen at 1 mg/L. These are health-based primary standards for public water systems.
Private wells are not monitored the same way public systems are. That is why EPA recommends annual private-well testing for nitrate along with total coliform bacteria, total dissolved solids, and pH. If the source is a private well, the well owner has to arrange testing and decide follow-up with local guidance.
For well context, use the Private Well Water Guide.
Who should be most cautious
Infants are the major risk group emphasized in official nitrate guidance. Pregnant people, people with specific health conditions, and immunocompromised people may also need more cautious water decisions under clinician or health-department guidance.
This article is not medical advice. If nitrate is high, if an infant uses the water, or if anyone may be medically vulnerable, contact a local health department, clinician, or certified lab for next steps.
When to test for nitrate
Test for nitrate when:
- your drinking water comes from a private well
- the well is near farms, fertilizer use, livestock, feedlots, or manure storage
- the well is near a septic system
- flooding or heavy runoff affected the area
- a new baby will use the water for formula or drinking
- local health agencies recommend nitrate testing
- the water source is a spring or outdoor source used for drinking
Are nitrate strips enough?
Nitrate strips can be useful as a first screen, but they are not the best final proof when drinking decisions or infant use are involved. The result can be affected by strip quality, timing, color reading, and the range printed on the chart.
If a strip suggests nitrate is elevated, or if the source has real nitrate risk, use When To Lab Test Water. A certified lab report is easier to interpret against EPA standards and local guidance.
For strip limits in general, read Water Test Strips Explained.
Nitrate and filters
Not every filter removes nitrate. Taste filters and pitcher filters are often built around carbon, and carbon is not a universal nitrate solution. Some systems, including properly designed reverse osmosis or ion-exchange systems, may reduce nitrate depending on certification, design, installation, and maintenance.
The safe sequence is test first, then choose treatment. Match the treatment to the contaminant and verify the product claim. After installation, retest or monitor as recommended.
For treatment context, use the Water Filter Guide and Reverse Osmosis Water.
What to do after a nitrate result
If a lab result is below the applicable standard and the well has no new risk, keep the report as a baseline and test again on schedule. If a result is high, close to the standard, rising over time, or tied to infant use, contact a local health department or certified lab before relying on the water.
Do not boil water to remove nitrate. Boiling can concentrate dissolved substances as water evaporates. Use local health guidance for immediate drinking-water decisions and treatment planning.
Practical takeaway
Nitrate is invisible to your senses and easy to miss with the wrong tool. Private well owners should test for it regularly, especially near agriculture, septic systems, flooding, or infant use.
Use nitrate strips as a screen at most. Use lab testing when the result affects drinking, treatment, or health-sensitive use.
