Nitrate and bacteria: is my well water safe?
The two most common health problems in private wells, explained, with a quick checker for your result.
Nitrate
Nitrate comes from fertilizer, manure and septic systems, and can't be seen, tasted or smelled. The EPA limit is 10 mg/L as nitrogen. Babies under 6 months are most at risk: high nitrate reduces how well their blood carries oxygen ("blue baby syndrome"). Boiling does not remove nitrate; it concentrates it.
Coliform bacteria and E. coli
Total coliform bacteria show that surface water or soil can reach your well. E. coli means fecal contamination and a real risk of illness. If E. coli is found, don't drink the water untreated; use bottled water or boil it, find and fix the cause, shock-chlorinate and retest. Shock chlorination calculator.
After a flood
Floodwater can carry bacteria and nitrate into wells. EPA says not to drink the water until a test shows it is safe. See flood alerts.
Questions
Can I boil water with high nitrate?
No. Boiling does not remove nitrate and makes it more concentrated as water evaporates. Use another water source for infants.
Is total coliform dangerous?
Total coliform alone is a warning that the well may be open to contamination. E. coli is the stronger sign of risk. Both call for fixing and retesting.