Nitrates in Well Water — Safe Levels, Risks & Treatment

Nitrates are the most common chemical contaminant in private wells. They are colorless, odorless, and tasteless — impossible to detect without testing. At high levels they are dangerous for infants and concerning for pregnant women.

Nitrate Levels and What They Mean

Nitrate Level	EPA Status	Risk	Action
0–5 mg/L	Well below limit	Safe for all ages	No action needed
5–10 mg/L	Approaching limit	Safe for adults; monitor	Retest annually
10 mg/L	EPA Maximum Contaminant Level	Unsafe for infants under 6 months	Treatment required
10–20 mg/L	Above EPA limit	Dangerous for infants, concerning for pregnant women	Treat immediately
20+ mg/L	Significantly elevated	Serious risk for all vulnerable groups	Do not use for drinking or cooking

Why Nitrates Are Dangerous for Infants

Nitrates in the body convert to nitrites, which interfere with hemoglobin's ability to carry oxygen. In infants under 6 months, this causes methemoglobinemia — also called "blue baby syndrome." The infant's skin turns bluish from oxygen deprivation. This condition can be fatal if not treated promptly.

Adults have stomach acid that prevents nitrite formation; infants do not. Adults can safely drink water at 10 mg/L that would be dangerous for an infant.

Where Nitrates Come From

• Agricultural fertilizer — the leading source in rural areas. Nitrates from fertilizer leach through soil into groundwater.
• Septic systems — particularly failing or undersized systems near the well.
• Livestock operations — manure application and runoff.
• Natural decomposition — organic matter breakdown in the soil contributes low background levels.

Treatment Options

Reverse Osmosis (Most Practical)

A point-of-use reverse osmosis system installed under the kitchen sink removes 85–95% of nitrates. This is the most cost-effective solution for most households — it treats the water at the tap where you drink and cook. Cost: $200–$500 for the unit, plus annual filter replacement ($50–$100). Does NOT protect bath water — not a concern for adults but be cautious with infant baths at very high levels.

Ion Exchange (Nitrate-Specific)

A whole-house ion exchange system (different from a standard water softener) removes nitrates throughout the home. Cost: $1,000–$3,000 installed. Higher upfront cost but whole-house protection.

Distillation

Distillation removes nitrates completely but is slow and produces small amounts of water. A countertop distiller costs $150–$400. Best as a temporary solution.

If You Have an Infant

If your nitrate level exceeds 10 mg/L and you have an infant under 6 months, use bottled water for formula and all infant food preparation immediately. Install a reverse osmosis system as soon as possible. Retest the well annually — nitrate levels fluctuate seasonally with rainfall and agricultural cycles.