Bacteria in Well Water: Coliform Testing & Disinfection

Types of Bacteria Tests

Total coliform: Indicator organisms that suggest potential contamination pathways. A positive result does not necessarily mean harmful bacteria are present, but indicates the well may be vulnerable. E. coli: Presence confirms fecal contamination and immediate health risk. Heterotrophic plate count: Measures overall bacterial activity.

Common Sources

Bacterial contamination enters wells through: cracked well casings, improper well caps, surface water infiltration, nearby septic systems, animal activity near the wellhead, and flooding events.

What to Do After a Positive Test

1. Do not drink the water without boiling. 2. Shock chlorinate the well (pour chlorine bleach solution down the well). 3. Retest after 1-2 weeks. 4. If positive again, inspect the well for physical defects. 5. Consider UV disinfection or continuous chlorination for persistent problems.

Prevention

Maintain a 50-foot setback from septic systems. Keep the wellhead above grade and properly sealed. Inspect annually. Divert surface drainage away from the wellhead.