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Backflow Incidents
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Backflow Incidents

Many backflow incidents occur that are not reported.  This is usually because:
  • The incidents are of short duration;
  • The incidents are not detected;
  • The customer is not aware the incident should be reported;
  • Customers do not know who to report the incident to; and / or
  • Liability concerns on the part of the customer.

If you have any knowledge of a backflow incident, please contact your local water purveyor.

How Can I Determine if Backflow Has Occurred?

Customer complaints of changes in water quality—such as unusual odor, color, or tasteor physical harm from water contact can indicate backflow. Water-system personnel handling quality complaints should be well-educated about backflow so that they can identify potential incidents. Water operators may note a drop in operating pressure, lowered chlorine residual, a spike in coliform detections, or water meters running in reverse, any of which may indicate that backflow has occurred. 


However, it is very difficult to determine whether any of these occurrences are due to backflow. Backflow incidents may not be detected for many reasons, such as:

  • Bacterial contamination is usually transient and localized, so sampling may not detect it.
  • Chemical and bacterial monitoring is not thorough or frequent enough to identify most backflow incidents.
  • Not all contamination can be detected by color, odor or taste, so it passes unreported by customers.
  • Water system operators may not report suspected backflow incidents due to concerns about liability and loss of consumer confidence.
  • Customers may not report all irregularities in water quality.
  • Incidents of reduced pressure in water distribution systems are often transient and difficult to detect by conventional pressure-monitoring equipment, and may be localized. Reduced pressure is often due to routine flushing or line breaks.
  • Health effects are difficult to link to backflow incidents, especially chronic effects.
  • Contamination may not be widespread enough to draw the attention of public health officials.
  • Information that could link an outbreak of illness to a backflow incident is often lacking.

It is important to encourage industrial and residential customers to report backflow incidents to the public water system immediately.

Sample Incident Report Form

The backflow incidents reported in this document are provided to give the reader an appreciation of the potential for contamination of a potable water system.  It is not the intent of these documents to provide an in-depth account of each incident.  Each incident is a summary of information obtained from one or more sources.  Source information was accepted as accurately reflecting the backflow incident.  When subsequent information on an incident is obtained, the additional information is given as a 'postscript' to the original incident report.  For any use of the material contained in this document for purposes other than the one stated above, the reader is responsible for confirming the accuracy of the backflow incident report.

2016 -  Chemical is Back Pressured into City Water Supply - Corpus Christi, TX

2016 - Thousands Told to Boil Drinking Water - Ft. Worth, TX  

2015 - Water System Blamed in Legionnaire's Outbreak - St. Louis, MO  

2015 - Drinking Water Fountain Found Connected to Recycled System - Cranbourne, Australia   

2015 - Pink Water Causes Hardship for Palmetto - Village of Palmetto, LA  

2015 - Contractor Error Cause of Contamination, Pays City for Backflow Action - Lockport, NY  

2015 - Sprinkler System Suspected of E-Coli Contamination - Corpus Christi, TX

2012 - Backflow Incident at a Swimming Pool - Liddieville, LA

2012 - Backflow Contamination in City Drinking Water - Boca Raton, CA 

2012 - Family Wins Lawsuit Over Drinking Water Connected to a Sewer Line - Commerce City, CO

2010 - Water Fountain Contamination at Elementary School - Queens, NY

2010 - Boil Water Order Issued in 30 Massachusetts - Boston, MA

2010 - Poor Water Quality at Meat Processing Plant2010 - Poor Water Quality at Meat Processing Plant

2010 - Sewage Pump Hooked up to Municipal Drinking Water System - Mactier, Ontario

2010 - Well Contaminates Water District Systems with E-Coli - Motueka, Australia

2010 - Plumber Quits After Tainting Water - St. Paul, MN

2010 - Glycol Contaminates School Water - Bowling Green, KY

2010 - Problems with Valve Shuts off Drinking Water at High School - Baltavia, IL

2010 - Governor Declares Emergency Over Water Contamination - Barstow, CA

2010 - E-Coli Bacteria Found in Water Supply - Winslow Township, NJ

2009 - Water Contaminated at High School - Floyd County, VA

2009 - Water Contaminated with E-Coli - Cook City Water District, MT

2009 - Soda Machine Blamed in Illness at Restaurant - Lenexa, KS

2008 - Fire Foam Contaminates Water Supply - Pittsburgh, PA

2008 - Bacteria Found in Stafford Water - West Linn, OR


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