Nitrate in Tap Water
Nitrate is a nitrogen compound that enters water mainly from fertilizer, animal waste, and septic systems. It is one of the most common contaminants in agricultural areas.
Runoff and leaching from fertilizer, manure, and septic systems into groundwater and surface water.
- 1Agricultural fertilizer
- 2Animal feedlots and manure
- 3Septic systems
Most affected: Infants under six months (risk of methemoglobinemia, "blue-baby syndrome") and pregnant people.
A result is read with its context
This contaminant is tracked through federal and state compliance monitoring. Private wells near farmland should be tested, especially before use by infants. PurityMap does not yet publish a per-system measured value for Nitrate; this page is a reference explainer. To learn what is in your own water, check your utility’s Consumer Confidence Report (CCR) or use a certified home test.
- Above reference
- Evidence exceeds a reference level.
- Detected
- This substance was found in the monitoring record. Being present is not the same as being above a reference level, and this signal does not say which.
- Not detected
- Somebody looked and the laboratory reported nothing above its reporting limit. This is a result, and it is not the same as nobody looking.
- Not monitored
- No sampling for this substance has been reported for this system. Nothing is known either way, and an empty row is not a clean one.
21 cities with a published nitrate result
- BoiseID · 2023 · Utility report5.6 mg/LView city →
- PhiladelphiaPA · 2025 · Utility report5.3 mg/LView city →
- AllentownPA · 2025 · Utility report4.96 mg/LView city →
- Fort WayneIN · 2025 · Utility report4.774 mg/LView city →
- OmahaNE · 2025 · Utility report3.19 mg/LView city →
- LincolnNE · 2025 · Utility report0.91 mg/LView city →
- FriscoTX · 2025 · Utility report0.866 mg/LView city →
- DallasTX · 2024 · Utility report0.834 mg/LView city →
- MinneapolisMN · 2024 · Utility report0.67 mg/LView city →
- BostonMA · 2025 · Utility report0.64 mg/LView city →
- Las VegasNV · 2025 · Utility report0.5 mg/LView city →
- Jersey CityNJ · 2023 · Utility report0.4 mg/LView city →
- Los AngelesCA · 2025 · Utility report0.4 mg/LView city →
- NormanOK · 2025 · Utility report0.378 mg/LView city →
- DurhamNC · 2024 · Utility report0.33 mg/LView city →
- ChattanoogaTN · 2025 · Utility report0.31 mg/LView city →
- WorcesterMA · 2025 · Utility report0.291 mg/LView city →
- TampaFL · 2025 · Utility report0.29 mg/LView city →
- New York CityNY · 2025 · Utility report0.14 mg/LView city →
- DenverCO · 2025 · Utility report0.1 mg/LView city →
- OrlandoFL · 2024 · Utility report0.09 mg/LView city →
Latest published value per city, from Utility report. A system-level result, not a measurement of any single home.
+8 more states.
20 cities with a health-based violation
A violation is a past event with a status, from the federal compliance record (EPA SDWIS, since 2016). It does not describe the water today.
- BurkburnettTexasArchivedView city →
- East HempfieldPennsylvaniaResolvedView city →
- FlorenceArizonaResolvedView city →
- GuymonOklahomaResolvedView city →
- McFarlandCaliforniaResolvedView city →
- NewmanCaliforniaResolvedView city →
- HastingsNebraskaResolvedView city →
- Dodge CityKansasResolvedView city →
- YucaipaCaliforniaResolvedView city →
- ExeterCaliforniaResolvedView city →
- GilroyCaliforniaResolvedView city →
- HastingsMinnesotaResolvedView city →
- PocatelloIdahoResolvedView city →
- RiverbankCaliforniaResolvedView city →
- GrandviewWashingtonResolvedView city →
- EspañOlaNew MexicoResolvedView city →
- Atascosa RuralTexasResolvedView city →
- La Verne City WdCaliforniaResolvedView city →
- San Tan ValleyArizonaResolvedView city →
- TurlockCaliforniaResolvedView city →
What can carry a nitrate reduction claim
- Reverse osmosis
Semi-permeable membrane separation removing dissolved minerals, heavy metals, and persistent fluorinated chemicals down to 0.0001 microns.
- Anion exchange
Synthetic polyvalent resin beads that exchange unwanted dissolved ionic contaminants for harmless benchmark ions.
- Distillation
Boiling does not remove a dissolved chemical compound and can concentrate it. Many pitcher and refrigerator filters carry no verified claim for a compound like this at all.
A finding establishes the need, the need names the capability, the capability requires a verified certification. No product appears before that sequence completes. Filter Finder →
Frequently asked
Answers cite the same records as the page. How PurityMap analyzes water data
Nitrate is a nitrogen compound that enters water mainly from fertilizer, animal waste, and septic systems. It is one of the most common contaminants in agricultural areas.
The enforceable federal limit is 10 mg/L as nitrogen (MCL). The published health benchmark reads: 10 mg/L (as N) federal limit (MCL). PurityMap reads every measurement against its stated benchmark and never sets its own.
Agricultural fertilizer, Animal feedlots and manure, Septic systems.
High nitrate is an acute risk for infants: it interferes with the blood’s ability to carry oxygen. Levels can spike seasonally with irrigation and rainfall, so one low reading is not a guarantee. Boiling concentrates nitrate rather than removing it.
Treatment technologies commonly certified to reduce Nitrate include Reverse osmosis, Anion exchange, Distillation. Match the exact certified claim to your water before buying. Holding a format is not the same as holding the claim.
In PurityMap's published record, 21 cities have a published Nitrate value from utility Consumer Confidence Reports. This is the scope of our record, not a national prevalence estimate.
In the federal compliance record (EPA SDWIS, since 2016), 20 cities in PurityMap's record across 11 states had a water system measure Nitrate above the legal limit, most recently in 2026, including Burkburnett, TX; East Hempfield, PA; Florence, AZ. Each violation is a past event with a published status, not a description of the water today.