Nitrate in Well Water
Nitrate enters groundwater from fertilizer, animal waste and septic systems, making it one of the most widespread private-well contaminants — especially in agricultural areas. Like arsenic, it's invisible and tasteless.
Why it's dangerous
High nitrate is most dangerous for infants under six months: it interferes with the blood's ability to carry oxygen, causing "blue baby syndrome" (methemoglobinemia). Pregnant women and adults face risks at sustained high levels too. Never mix infant formula with well water that hasn't been tested for nitrate.
The EPA limit
The federal MCL for nitrate (measured as nitrogen) is 10 mg/L. Boiling water does not help — it concentrates nitrate, making it worse.
States with the highest modeled risk
Share of private-well residents above the 10 mg/L limit (USGS model):
- Delaware 12.7%
- California 10.4%
- Maryland 6%
- Oklahoma 6%
- Kansas 5.2%
- Pennsylvania 3.9%
- Idaho 3.7%
- Texas 2.5%
How to remove nitrate
Carbon filters and standard softeners do not remove nitrate. Use reverse osmosis (NSF/ANSI 58) or a nitrate-specific anion-exchange system. Reverse osmosis is the simplest point-of-use fix for drinking and cooking water.
Match the filter to your test result
Carbon pitchers and faucet filters do not remove arsenic or nitrate. Reverse osmosis is the point-of-use fix; a whole-house system handles the rest of the home.
APEC ROES-50 5-Stage Reverse Osmosis System
5-stage RO, ★ 4.7 — removes arsenic, nitrate, lead, fluoride and PFAS.
Check price on Amazon →Whole-house well water system
Treats every tap, shower and appliance — the right scale for sediment, iron, sulfur and bacteria on a private well.
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Under-sink RO removes arsenic, nitrate, lead and PFAS at the kitchen tap.
Shop on Waterdrop direct →Affiliate links — we may earn a commission at no extra cost to you. Re-test after installing to confirm the system is working.