Nitrate in Well Water
Nitrate has no taste or smell and it is dangerous to infants at levels that are common under farmland and near septic systems. It is the one result on a report that changes what a family does today.
Likely causes
- Fertilizer on cropland or lawns
- Septic systems and manure
- Shallow wells in sandy soil
- Natural nitrogen in a few aquifers
Tests to order
- Nitrate as nitrogen
- Nitrite
- Total coliform
- Pesticides if farmland is nearby
Treatment options
- Reverse osmosis at the kitchen tap
- Anion exchange whole-house unit
- Distillation
- Deepen or relocate the well
Why 10 is the number
The federal limit is 10 mg/L of nitrate as nitrogen. Above it, infants under six months can develop methemoglobinemia, blue baby syndrome, because nitrate interferes with how their blood carries oxygen. Pregnant women and people with certain enzyme deficiencies are also at risk. Adults tolerate higher levels, but long-term exposure is under study for other effects. Nitrate is invisible, tasteless and not removed by boiling, which concentrates it.
Where it comes from on your property
Nitrate is nitrogen fertilizer, manure and septic effluent that rain has carried into shallow groundwater. Wells under 100 feet in sandy or gravelly soil are the most exposed. Test in late spring after fertilizer season and again in fall to see the range, because levels swing with the farming calendar.
Treating it
Reverse osmosis at one tap removes 80 to 95% of nitrate for the water you drink and cook with, $300 to $800 installed, and is the standard answer for most homes. Whole-house anion exchange units treat every tap but cost more and need salt. Distillers work but are slow. If a well is shallow and the level is far over the limit, a deeper well cased past the shallow aquifer is often the lasting fix.
Can I use nitrate water for formula?
No. Use bottled water or RO-treated water for any infant formula until a test shows nitrate under 10 mg/L.
Does a water softener or carbon filter remove nitrate?
Neither does. Only reverse osmosis, anion exchange or distillation remove it.