Coliform bacteria in well water
The Minnesota Department of Health explains that total coliform bacteria are an indicator: if found, surface contamination may have reached the water and germs may be present.
What a positive result means
Texas A&M AgriLife Extension says E. coli or fecal coliform in well water means the water has contacted human or animal waste and could cause disease.
After a positive total coliform result, Texas A&M advises collecting a new sample and testing it for fecal coliform or E. coli, since the first sample may have been contaminated during collection.
Until the retest comes back, Texas A&M advises using bottled water for drinking and cooking, or boiling water if bottled water is not available.
Texas A&M advises finding the cause first (wellhead, septic, nearby old wells, animal waste), then shock chlorinating, then retesting before drinking the water untreated.
Tennessee advises that a well testing positive for bacteria be disinfected and retested, and that persistent bacteria may need permanent disinfection equipment.
The Minnesota Department of Health says germs signalled by coliform can cause diarrhea, vomiting, cramps, nausea and fever, and are most dangerous for infants, children, the elderly and people with weak immune systems.
Sources: What coliform bacteria indicate; E. coli means waste contact; Tennessee: disinfect and retest
Common questions
What does a positive coliform test mean?
The Minnesota Department of Health explains that total coliform bacteria are an indicator: if found, surface contamination may have reached the water and germs may be present.