What the number means
EPA's limit is 10 mg/L as nitrogen. Some labs report nitrate as NO3 instead: divide that number by 4.43 to get the nitrogen number.
Minnesota Department of Health says babies under six months should not drink well water with nitrate above 10 mg/L, and suggests bottled water as a safe alternative.
Why it matters most for babies
Nitrate in water can keep a baby's blood from carrying enough oxygen. The condition is called methemoglobinemia, or blue baby syndrome, and it is why the limit protects babies under six months first. Minnesota Department of Health says to use bottled water for a baby's drinking water and formula when a well is above the limit.
Nitrate has no taste, color or smell. Only a lab test shows it.
Where nitrate in a well comes from
- Fertilizer used on nearby fields, lawns or gardens.
- Animal manure from feedlots and pastures.
- Household wastewater that leaks or drains near the well.
- Natural sources, at lower levels.
Nitrate-N and NO3: the same limit in two units
Check which unit your lab report uses before you compare it to the limit.
| Nitrate as nitrogen (NO3-N) | Same amount as nitrate (NO3) |
|---|---|
| 2 mg/L | about 9 mg/L |
| 5 mg/L | about 22 mg/L |
| 10 mg/L (the EPA limit) | about 44 mg/L |
| 20 mg/L | about 89 mg/L |
What to do if it is high
- Use bottled water for babies and for drinking. Do not boil the water: boiling makes nitrate more concentrated.
- Have a licensed well contractor inspect the well, and find and remove nearby nitrate sources first.
- If that does not fix it, home treatment is an option: reverse osmosis, distillation or anion exchange, kept up so they keep working. A water softener does not reduce nitrate.
- Even with treatment, keep babies under six months off the water.
How to test
EPA says to test a private well every year for total coliform bacteria, nitrates, total dissolved solids and pH. Use a state-certified lab, and ask whether the result is nitrate-N or NO3.
Questions
Is nitrate in well water a risk for adults?
The limit is set to protect babies under six months first. If your result is above 10 mg/L as nitrogen, keep infants and formula off the water, and ask your health department what else to do.
Can I tell if my well has nitrate by the taste?
No. Nitrate has no taste, color or smell. Only a lab test shows it.
Does boiling remove nitrate from well water?
No. Boiling makes nitrate more concentrated, according to the Minnesota Department of Health. Use bottled water instead.
Does a water softener remove nitrate?
No. The Minnesota Department of Agriculture says a softener does not reduce nitrate. Reverse osmosis, distillation and anion exchange do, when they are maintained.
Next step
- Well water treatment picker: the type of system that fits your results
- Well water test results explained: enter your lab numbers and get a next step
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