Water Knowledge

E. coli

Summary: Escherichia coli (E. coli) lives in the intestines of humans and warm-blooded animals. Finding E. coli in drinking water is a clear sign of recent fecal contamination and means the water is unsafe to drink until corrected and confirmed safe.

Why homeowners should care

E. coli is a red-flag indicator for pathogens. If it’s in your water, harmful microbes may be present too. Immediate action is needed—especially to protect infants, children, older adults, and anyone with a weakened immune system.

Where E. coli contamination comes from

  • Septic system failures: Leaks, saturated drain fields, or systems installed too close to a well.
  • Agricultural runoff: Manure application or livestock near the wellhead.
  • Wildlife/household animals: Animal waste near springs, cisterns, or poorly sealed wells.
  • Sewage events: Broken mains, backflows, or floodwaters entering the well.

When to test

  • Annually for private wells (minimum).
  • After floods, heavy rains, or droughts.
  • After well, pump, or plumbing work.
  • Any time taste/odor/clarity changes or illness is suspected.

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 straightforward: “Detected” or “Not Detected.” E. coli “Detected” = unsafe.

How to collect a good sample

  • Use the kitchen cold-water tap (or primary drinking tap).
  • Remove aerators/screens; sanitize the spout if instructed.
  • Run cold water for several minutes to flush.
  • Do not touch the inside of the bottle or cap; fill to the line.
  • Keep the sample cold and deliver promptly.

What to do if E. coli is detected

  1. Stop using the water for drinking/cooking right away. Use bottled water or boiled water for drinking, food prep, brushing teeth, and making baby formula.
  2. Inspect & correct the source: Check well cap/casing, sanitary seals, grading (drain water away from the well), and possible septic issues or flood impacts.
  3. Disinfect the system: Perform shock chlorination (per local guidance) and flush thoroughly until chlorine dissipates.
  4. Verify: Retest after the system returns to normal (often 1–2 weeks after chlorine is gone). Water must read Not Detected for E. coli before normal use resumes.
  5. Consider continuous protection (if recurring): UV disinfection or properly managed chlorination after fixing structural issues.

FAQ

Is all E. coli harmful?

Not every strain causes illness, but any E. coli in drinking water is treated as unsafe because it signals fecal contamination.

Can I just boil the water?

Boiling makes water safe for immediate use (bring to a rolling boil for at least 1 minute; 3 minutes at elevations >6,500 ft). But boiling doesn’t fix the cause—inspect, disinfect, and retest.

Is it safe to shower or wash hands?

Normal showering and handwashing are generally low risk for healthy adults. Avoid swallowing water. For infants or immune-compromised people, consider bottled/boiled water for hygiene until resolved.

How long after shock chlorination should I retest?

After chlorine dissipates and the system returns to normal use—often 1–2 weeks. Retesting too soon can give misleading results.

Do carbon or sediment filters remove E. coli?

Standard filters are not reliable for microbes. Use boiling, UV, or properly managed chlorination—and correct the contamination source.

My well flooded—what now?

Assume contamination. Use bottled/boiled water, inspect the well, disinfect the system, and retest when conditions stabilize.

What is a cross-connection?

A point where contaminated water can flow back into household plumbing (e.g., a hose submerged in a bucket). Install backflow preventers and keep hose ends above water.

Should I test multiple taps?

Start with the main kitchen cold-water tap. If E. coli is found, you can test strategic locations to help pinpoint whether the issue is the well or plumbing.

Do I need a whole-home system?

Not always. First fix structural issues (well cap, casing, drainage, septic). If contamination recurs, consider UV or continuous chlorination after the system is sealed.

Is ice safe?

No. Discard ice made during contamination. Make new ice only after a safe (Not Detected) result.

What about pets?

Use bottled/boiled water for pets too until the water tests safe. Animals can also get sick from contaminated water.

How often should I test going forward?

Annually at minimum for private wells, plus after floods, plumbing/well work, or any unusual changes. Consider seasonal checks if your area is prone to runoff.

Need a reliable bacteria test? Order a kit and get step-by-step sampling instructions at HealthWaterLab.com.