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Problem GuideColiform Action Plan

Coliform in Well Water: Your Step-by-Step Action Plan

A positive coliform test doesn't have to be a crisis — if you act correctly. Here's exactly what to do, in order.

Immediate action

Stop drinking unfiltered well water until resolved

If your test shows E. coli specifically, treat this as urgent — E. coli indicates fecal contamination. For total coliform without E. coli, the risk is lower but still needs resolution. Use bottled water for drinking and cooking until you've completed shock treatment and gotten a clean retest.

Your action plan — in order

  1. Stop drinking untreated well water — use bottled water for drinking, cooking, and making ice
  2. Don't panic — coliform contamination is common and fixable
  3. Identify the source — check for flooding near the well, inspect the well cap for damage, note if there's a nearby septic system
  4. Shock chlorinate the well — see guide below
  5. Flush the system — run every faucet until chlorine smell is gone
  6. Wait 1–2 weeks and retest — don't retest immediately after shocking, chlorine residual creates false negatives
  7. If test is still positive: call a licensed well contractor — structural issue with the well needs professional assessment
  8. Install permanent treatment — UV system to prevent future contamination

How to shock chlorinate your well

  1. Calculate water volume: for a 6-inch diameter well, multiply depth (feet) × 1.47 = gallons
  2. Use regular unscented household bleach (5.25–8.25% sodium hypochlorite)
  3. Add approximately 1 cup bleach per 100 gallons of water in the well
  4. Pour bleach solution into the well casing
  5. Connect a garden hose to an outdoor faucet and recirculate water back into the well for 15–20 minutes
  6. Open each indoor and outdoor faucet until you smell chlorine, then close
  7. Let sit for minimum 12 hours (24 hours preferred)
  8. Flush all faucets until chlorine smell is completely gone
  9. Wait 1–2 weeks before retesting

Why coliform keeps coming back

If your well tests positive repeatedly after shock chlorination, the source of contamination is ongoing:

These structural issues need to be fixed by a licensed well contractor — no filter system alone solves a well that's continuously taking in contaminated surface water.

Permanent treatment: UV disinfection

A UV (ultraviolet) disinfection system installed on your main water line kills bacteria, viruses, and cysts in real-time — 99.99% reduction without chemicals. This is the standard permanent solution after coliform contamination is resolved.

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