Total Coliform
Summary: Total coliforms are a group of bacteria naturally found in soil, plants, and surface water. They are not usually harmful on their own, but if they show up in your drinking water, it signals that contaminants can get in—and that disease-causing microbes might follow. Testing tells you if your well or plumbing needs attention.
Why homeowners should care
Total coliforms are an early warning light. Their presence often means there’s a pathway for contamination: a loose well cap, a cracked casing, a flooded wellhead, or cross-connections in plumbing. Catching and fixing that pathway reduces the risk of E. coli and other pathogens.
Where total coliforms come from
- Surface water influence: Rain, snowmelt, or runoff entering the well or spring.
- Well construction issues: Damaged or shallow well cap, cracked casing, poor sanitary seal, missing vermin screen.
- Septic impacts: Failing or too-close septic systems, or saturated drain fields.
- Plumbing cross-connections: Garden hoses submerged in buckets, untreated bypass lines, or faulty backflow devices.
When to test
- Annually for private wells (at minimum).
- After floods, heavy rains, or droughts.
- After pump/well/plumbing work or disinfection.
- Any time you notice changes in taste, odor, color, or pressure.
How we test
HealthWaterLab uses a presence/absence method (e.g., Colitag) that reports both total coliform and E. coli in a single analysis. Results are clear: “Detected” or “Not Detected.” The method is designed for drinking water and is highly sensitive.
How to collect a good sample
- Choose the kitchen cold-water tap (or the tap you drink from most).
- Remove aerators/screens; sanitize the spout if instructed.
- Run cold water several minutes to flush standing water.
- Don’t touch the inside of the bottle or cap; fill to the marked line.
- Keep the sample cold and deliver to the lab promptly.
How to read your result
- Not Detected: No total coliforms found. Keep yearly testing and good well hygiene.
- Total Coliform Detected (E. coli Not Detected): Fix pathways (well cap/seals, drainage, plumbing cross-connections), disinfect, then retest.
- E. coli Detected: Treat as unsafe. Use bottled/boiled water for drinking/cooking until corrected and confirmed safe by retesting.
What to do if total coliforms are detected
- Inspect & repair: Check the well cap, casing, sanitary seal, and grading. Make sure surface water drains away from the well.
- Disinfect: Perform well/system disinfection (shock chlorination) per local guidance; flush thoroughly.
- Control sources: Address septic issues, relocate animal pens, add/repair backflow devices, fix cross-connections.
- Verify: Retest after corrections. Consider a second confirmatory test a week or two later.
- Consider continuous protection (if recurring): Ultraviolet (UV) disinfection or chlorination systems after solving structural issues.
FAQ
Are total coliforms themselves dangerous?
Usually not. They are indicators that contamination pathways exist. Their presence raises the risk that harmful microbes could also get in.
How fast should I act if total coliforms are detected?
Act promptly: inspect, disinfect, and retest. Quick action reduces the chance of E. coli showing up later.
Does boiling make the water safe?
Boiling kills bacteria for immediate use, but it doesn’t fix the underlying problem. Correct the source and verify with a lab retest.
Why did I pass last year but fail this year?
Well conditions change—storms, drought, construction, or a loose cap can create new pathways. That’s why annual testing matters.
What’s the difference between total coliform and E. coli?
Total coliforms are broad indicators; E. coli signals recent fecal contamination and is considered unsafe for drinking.
Do I need a whole-home treatment system?
Not always. First fix the structural issues (well cap, casing, drainage). If problems recur, consider UV or chlorination after the system is sealed.
Can filters remove coliform bacteria?
Standard carbon/sediment filters are not reliable for microbes. Use boiling, UV, or properly maintained chlorination when needed—and fix the source.
How long after shock chlorination should I retest?
Follow local guidance; many homeowners wait 1–2 weeks after chlorine dissipates to ensure results reflect normal conditions.
Is a spring or cistern more likely to have coliforms?
Yes—surface influence raises risk. Tighten lids, screens, and sanitary features, and consider UV after fixing openings.
What is a cross-connection and why does it matter?
It’s a point where contaminated water can flow back into your plumbing (e.g., a hose submerged in a bucket). Use backflow preventers and keep hose ends above water.
Should I test multiple taps?
Start with the main kitchen cold-water tap. If a problem is found, you can test strategic locations to pinpoint whether the issue is the well or the household plumbing.
Can I rely on test strips instead of a lab test?
No—home strips are not sensitive/specific enough for drinking water decisions. Use a lab presence/absence test for clear results.
Need a reliable bacteria test? Order a kit and get step-by-step sampling instructions at HealthWaterLab.com.