The EPA limit for nitrate in drinking water is 10 mg/L as nitrogen. Above that level, infants under six months and pregnant women should not drink the water — and boiling it makes nitrate more concentrated, not less. Nitrate is tasteless, odorless, and invisible, which is why it's one of the two tests every well owner runs annually. Here's what the number means, where it comes from, and the short list of treatments that actually remove it.
Reading your number
Labs report nitrate two ways, and confusing them is a common scare (or a common false comfort): 10 mg/L as nitrate-nitrogen (NO₃-N) is the EPA standard, which equals 45 mg/L as nitrate (NO₃). Check which unit your report uses before deciding anything. Results that creep from 2 to 5 to 8 over successive annual tests are the well telling you something is loading nitrogen upstream — the trend matters as much as the threshold.
Who's at risk, and why
- Infants under 6 months: nitrate converts to nitrite in a baby's gut and interferes with the blood's oxygen carrying — methemoglobinemia, "blue baby syndrome." It's rare, serious, and entirely avoidable: formula and drinking water for infants from a source under 10 mg/L, period.
- Pregnant women: the same precaution applies during pregnancy.
- Everyone else: the 10 mg/L standard is set for the most vulnerable; adults tolerate more without acute effects, but long-term high exposure is under active research and no one should treat an exceedance as background noise.
Where nitrate comes from
Nitrogen from the surface that soil didn't fully capture: fertilized fields and lawns, livestock operations and manure storage, and septic systems — including yours, if the drainfield sits too close to the well, upslope of it, or is failing. Shallow and dug wells in sandy soil are the most exposed; readings often spike after spring rains flush fields. Nitrate frequently travels with bacteria — a nitrate hit is a reason to look at the whole panel.
What removes nitrate — and what doesn't
| Method | Removes nitrate? | Cost / notes |
|---|---|---|
| Boiling | 🚫 Concentrates it | The dangerous "fix" |
| Carbon / pitcher filters | 🚫 No | Taste only |
| Water softener | 🚫 No | Hardness only |
| Reverse osmosis (kitchen tap) | ✅ 80–95% | $300–$1,500 — the standard answer for drinking/cooking |
| Anion exchange (whole house) | ✅ Yes | $1,500–$4,000; needs correct resin and maintenance |
| Distillation | ✅ Yes | Slow; small volumes |
| New/deeper well or connection | ✅ Source change | When loading is chronic — costs here |
Whatever you install, retest after installation and yearly — RO membranes and resins degrade, and the nitrate source is still out there. Our treatment cost guide covers where RO sits in an equipment chain.
Fix the source, not just the tap
Treatment protects your family; it doesn't stop the loading. Check your own septic system's distance and condition first (it's the source you can control), reconsider lawn fertilizer near the wellhead, and if agricultural neighbors are the likely origin, your state's environmental agency and county extension office often have nitrate programs and cost-share for testing and treatment in affected areas. (Testing for nitrate? Add arsenic to the same sample — the other tasteless contaminant most wells have never been checked for.)
Frequently Asked Questions
What level of nitrate in well water is safe?
The EPA drinking-water standard is 10 mg/L nitrate-nitrogen (equivalently 45 mg/L as nitrate — labs report both ways, so check the unit). Below 10 mg/L as N is considered safe for everyone; above it, infants under 6 months and pregnant women should not drink the water, and everyone should treat or switch sources.
Does boiling water remove nitrates?
No — it makes them worse. Boiling evaporates water and concentrates the nitrate left behind. The same is true of standard carbon filters and water softeners, which do not remove nitrate at all. Only reverse osmosis, anion exchange, or distillation remove it — or a different water source.
Where do nitrates in well water come from?
Nitrogen that reached groundwater from the surface: fertilizer on crops and lawns, livestock manure, and septic systems — including your own if it's too close, too old, or failing. Shallow wells, sandy soils, and agricultural areas carry the highest risk, and levels often peak after spring rains flush fields.
How do I remove nitrates from well water?
For drinking and cooking, a point-of-use reverse osmosis unit at the kitchen tap ($300–$1,500) is the standard fix and removes 80–95%. Whole-house anion exchange ($1,500–$4,000) treats every tap. Distillation works but is slow. Verify any system with a follow-up lab test — and find the nitrogen source, because treatment doesn't stop the loading.