A positive coliform test is alarming but fixable. Here's what it actually means, what the risk is, and how to treat it permanently.
If you've seen any coliform indicator (cloudy water, off-taste, recent flooding), confirm with a certified lab before treating. Tap Score's coliform bacteria test gives you a definitive yes/no result and identifies whether E. coli is present — the difference matters for treatment urgency.
Order Coliform Bacteria Test (~$60) →A positive coliform result means bacterial contamination is present. Stop drinking unfiltered well water until the issue is resolved. Shock chlorination eliminates the current contamination. A UV system or continuous chlorination prevents recurrence. The source of contamination — surface water intrusion, a cracked casing, nearby septic — also needs to be identified.
Total coliform is a group of bacteria used as an indicator of water quality. Their presence doesn't necessarily mean sewage contamination — coliform bacteria exist naturally in soil and on vegetation. But their presence in well water indicates a pathway for surface water to enter your well, which could also allow pathogens to enter.
E. coli is a subset of coliform bacteria. A positive E. coli result specifically indicates fecal contamination — a more serious finding that requires immediate action.
| Total coliform positive, E. coli negative | Surface contamination likely — less severe, still needs treatment |
| Both total coliform and E. coli positive | Fecal contamination confirmed — requires immediate action, do not drink untreated water |
| E. coli positive alone | Rare — treat as fecal contamination |
Shock chlorination is a temporary disinfection — it kills current bacteria but doesn't prevent recontamination. A permanent solution is required.
| UV (ultraviolet) disinfection | Best option for most homes. UV light kills 99.99% of bacteria, viruses, and cysts without chemicals. Low maintenance, no ongoing chemical cost. Install on the main line after sediment filtration. |
| Continuous chlorination | Chlorine dosing pump injects small amounts of bleach into the water line. Effective but requires ongoing chlorine supply and a carbon filter downstream to remove taste/odor. |
| Reverse osmosis (point of use) | RO at the kitchen tap removes bacteria for drinking water only — doesn't treat whole house. Good addition but not a complete solution. |
Treating the symptom without fixing the source means it will recur. Common contamination sources:
A licensed well contractor can inspect your casing and seal. This is worth doing even after successful treatment — without fixing the source, contamination will return.
Springwell UV Systems →Kind Water WS-6000UV — Salt-free whole house system with UV
Handles hardness and bacterial disinfection in one pre-integrated unit. No salt, no chlorine — UV kills 99.99% of pathogens. Full review →
WS-6000UV — $3,222 at Kind Water →