High School Backflow Incident

The Incident:

In June 1984, a High School in New Mexico was shut down for several days when a home economics teacher noticed yellow-colored water flowing from the taps. Tests conducted by city chemists revealed dangerously high levels of chromium, measuring up to 700 parts per million—far exceeding the safe limit of 0.05 parts per million. The source of the contamination was identified as sodium dichromate, a highly toxic chemical used in the school’s heating systems to prevent corrosion.

What Happened:

The sodium dichromate entered the school’s drinking water supply due to backflow from the heating system. The cause was traced to leaky check valves on the boiler feed lines, which allowed the toxic chemical to flow backward into the potable water system. Fortunately, the contamination was detected before anyone consumed the water. Local hospitals and physicians were alerted to monitor for symptoms of exposure, such as nausea, diarrhea, and burning sensations in the mouth and throat. Immediate actions were taken to cover all water fountains before the school day began.

The Cross Connection:

The backflow occurred because of faulty check valves on the boiler feed lines, which failed to prevent the highly toxic sodium dichromate from contaminating the school’s drinking water. This direct cross-connection between the heating system and the potable water supply created a serious health risk.

Consequences and Actions Taken:

While no illnesses were reported, the incident highlighted the need for strict cross-connection control in school facilities. The faulty check valves were replaced with a proper backflow preventer, ensuring that hazardous chemicals from the heating system could no longer enter the school’s water supply.

Prevention Lesson:

This incident serves as a critical reminder of the importance of reliable backflow prevention in systems where hazardous chemicals are present. High-risk areas like commercial boilers and heating systems pose significant threats to drinking water supplies without proper safeguards. Installing correct backflow preventers, conducting regular inspections and maintenance, and enforcing cross-connection control programs are essential to protecting public health and ensuring safe water in educational facilities.

This story, originally written by Watts in "Backflow Case Histories and Solutions," has been summarized to highlight the key points and outcomes.