Restaurant Backflow Incident
The Incident:
On January 29, 1981, a well-known fast-food restaurant in Norfolk, Virginia, reported a serious issue to the Water Department: customers were rejecting beverages, including sodas, coffee, and orange juice, due to an unusual salty taste. A nearby ship-repair facility also complained of salty water, as both the restaurant and the shipyard were supplied by the same water-main lateral connected to the main distribution line.
What Happened:
A cross-connection control inspection revealed that the backflow preventer installed on the shipyard’s service line had frozen and burst earlier in the winter. To maintain water supply to the shipyard, the damaged backflow preventer was removed and temporarily replaced with a sleeve, eliminating any protection against backflow.
The Cross Connection:
The shipyard’s fire protection system operated using high-pressure seawater maintained by electric and diesel-driven pumps. The pumps were primed with city water directly connected to the high-pressure fire system. With the priming line left open, the seawater was pumped under positive pressure through the sleeve and into the public water distribution system, contaminating the water supplied to the nearby restaurant.
Consequences and Actions Taken:
The contamination affected beverages at the restaurant and created potential health risks. To correct the problem, the city water prime line to the shipyard pumps was disconnected, and a new backflow preventer was installed in place of the sleeve. To prevent future freezing and equipment failure, heat tape was wrapped around the newly installed backflow preventer.
Prevention Lesson:
This incident underscores the importance of maintaining properly functioning backflow prevention devices, especially in facilities handling hazardous or non-potable water sources. Regular inspections, appropriate repairs, and winterizing critical equipment can prevent costly and dangerous cross-connections in the future.
This story, originally written by Watts in "Backflow Case Histories and Solutions," has been summarized to highlight the key points and outcomes.