Loading water data...
Bacterial contamination poses immediate health risks and requires urgent attention. Learn about coliform bacteria, E. coli, testing requirements, and effective treatment options.
Bacteria are microscopic organisms found everywhere in nature. While most bacteria are harmless or even beneficial, certain types in drinking water can cause serious illness. Bacterial contamination typically indicates that water has been in contact with human or animal waste.
Public water systems use disinfection (usually chlorine or chloramine) to kill bacteria and maintain a residual that prevents bacterial regrowth. Private wells have no such protection and are at higher risk of bacterial contamination.
Critical: Unlike many contaminants that pose long-term risks, pathogenic bacteria can make you sick within hours to days. If you suspect bacterial contamination, stop drinking the water immediately and seek testing.
A large group of bacteria found in soil, plants, and animal/human intestines. Their presence indicates possible contamination pathways but doesn't necessarily mean the water is unsafe.
EPA Standard: No more than 5% of monthly samples can be positive
A subset of coliform bacteria specifically from human or animal intestinal tracts. E. coli presence confirms fecal contamination and indicates that harmful pathogens may also be present.
EPA Standard: Zero tolerance - any detection triggers immediate action
A dangerous strain that produces toxins causing severe illness. Most E. coli are harmless, but pathogenic strains can cause bloody diarrhea, kidney failure, and death.
Risk: Very serious - seek medical attention if exposed
E. coli testing serves as an indicator for other pathogens that are harder to test for:
Infants and young children: Developing immune systems, higher risk of dehydration and complications.
Elderly: Weakened immune response, higher mortality risk.
Immunocompromised: HIV/AIDS patients, cancer patients, transplant recipients at severe risk.
Pregnant women: Risk of complications affecting both mother and fetus.
Any detection of E. coli in drinking water triggers an immediate violation. The MCL and MCLG are both zero - no amount is acceptable.
Required action: Boil water notice, increased monitoring, identify and fix contamination source.
No more than 5% of monthly samples can test positive for total coliform. A positive coliform test requires follow-up E. coli testing.
Monthly testing: Frequency depends on population served - from 1 sample for small systems to 480+ for major cities.
All public water systems using surface water or groundwater under the influence of surface water must use filtration and disinfection. Groundwater systems must monitor for E. coli and add disinfection if found.
Failing septic systems, sewage line breaks, or sewage overflows can introduce fecal bacteria directly into groundwater or surface water sources.
Livestock operations, wildlife, and pet waste can contaminate water sources, especially after heavy rainfall that causes runoff into streams and shallow wells.
Cracked well casings, improper seals, or insufficient well depth allow surface water and contaminants to enter the well directly.
Floods can overwhelm water treatment systems and contaminate wells. After flooding, wells should be disinfected and tested before use.
Pipe breaks, low pressure events, or cross-connections in public systems can allow contamination to enter treated water.
Equipment failures, power outages, or running out of disinfectant chemicals can allow bacteria to survive and multiply in the system.
21+ million Americans rely on private wells with no EPA regulation or required testing. Wells are vulnerable to contamination from septic systems, agriculture, and flooding.
Small systems often lack resources for consistent treatment and monitoring. They account for the majority of drinking water violations.
Areas with high agricultural activity, many septic systems, and older infrastructure face higher contamination risk.
Flooding can contaminate both wells and public systems. Post-flood testing is essential.
Good news: Bacterial contamination is one of the most treatable water quality problems. Proper disinfection can eliminate bacteria effectively.
The most reliable method. Labs culture water samples to detect and identify bacteria. Results typically available in 24-48 hours.
Tests available: Total coliform, E. coli, fecal coliform. Many state health departments offer free or low-cost testing.
Presence/absence tests using growth medium. Simple to use but less precise than lab testing. Good for initial screening.
Limitation: Confirms presence but doesn't quantify bacterial levels. Follow up positive results with lab testing.
Sample Collection Tips:
Bring water to a rolling boil for at least 1 minute (3 minutes above 6,500 ft elevation). This kills bacteria, viruses, and parasites. Use boiled water for drinking, cooking, brushing teeth, and making ice.
Cost: Free but labor-intensive
Ultraviolet light damages bacterial DNA, preventing reproduction. Effective against bacteria, viruses, and parasites including chlorine-resistant Cryptosporidium.
Cost: $500-1,500 for whole-house systems; bulb replacement every 12 months
Chemical disinfection using chlorine. Can be continuous (chlorine injection) or periodic (shock chlorination for wells). Leaves residual protection.
Cost: Shock chlorination $50-150; continuous systems $500-2,000
Ozone is a powerful disinfectant that kills bacteria and improves taste without leaving chemical residue. More expensive than chlorine.
Cost: $1,000-3,000 for systems
Microfiltration (0.1-0.2 micron) and ultrafiltration physically remove bacteria. Often used in combination with disinfection.
Cost: $200-1,000 depending on type
Important:
Treatment addresses the symptom, not the cause. Identify and fix the contamination source (failing septic, cracked well casing, etc.) for a permanent solution.
Shock chlorination uses high concentrations of chlorine to disinfect a well and plumbing system. It's a common first step when bacteria are detected.
Use 2-3 gallons of unscented household bleach (5.25% sodium hypochlorite) per 100 gallons of water in the well. Your state extension service can help calculate.
Turn off power to pump. Remove well cap and pour chlorine solution directly into well. Scrub inside of casing if accessible.
Run water through all faucets until you smell chlorine. This ensures chlorine reaches entire plumbing system. Include hot water heater.
Let chlorinated water sit in well and pipes. Don't use water during this time. Longer contact time (24 hours) is more effective.
Run water through outdoor spigot (to avoid septic damage) until chlorine smell is gone. Then flush indoor faucets.
Wait at least one week before retesting. If bacteria return, the contamination source hasn't been addressed.
Generally yes, if you don't swallow any water. Healthy adults can shower in coliform-positive water. However, avoid bathing infants, elderly, or immunocompromised individuals in contaminated water.
Most household filters (Brita, PUR) do NOT remove bacteria effectively. You need UV disinfection, specific 0.2-micron filters, or chemical disinfection to kill bacteria.
Bacterial contamination often returns if the source isn't fixed. Common causes: failing septic, cracked well casing, surface water infiltration, recent heavy rains.
No. Total coliform is a broad group that includes E. coli. Coliform presence indicates possible contamination pathways. E. coli specifically indicates fecal contamination and is more concerning.
Symptoms can appear within hours to days depending on the pathogen and exposure level. E. coli O157:H7 typically causes illness within 2-5 days.
No. Freezing may slow bacterial growth but doesn't kill them. When ice melts, bacteria can become active again. Only heat, UV, or chemical disinfection reliably kills bacteria.
See your city's water quality report and check for bacterial violations in your area.
This information is provided for educational purposes only and is not intended as medical advice. If you suspect you've consumed contaminated water and are experiencing symptoms, seek medical attention immediately. Bacterial contamination is a serious health risk requiring prompt action. Always verify water safety through proper testing before use.