back siphonage


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back siphonage

A reversal of the normal flow of water or other liquid due to a negative-pressure gradient. Back siphonage in a water system may result in contamination, triggering a “boil order” (i.e., an order to boil water before drinking so as to kill potential contaminants).
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atmospheric pressure), back siphonage occurs and vacuum breakers are appropriate backflow prevention devices.
If the consumer has a private water supply or even reuses some of the city water for other purposes, definite precautions should be taken to prevent any possible back siphonage induced by opening a large valve on a lower floor, especially when the city line has low pressure, thus allowing a submerged inlet or hose on an upper level to siphon polluted water into the lines.
Most outbreaks involved private water supplies and were caused by direct fecal contamination, back siphonage from a nonpotable source into a potable system, or cross-connections between such systems.