SafetyQuestion 341 of 360
A water main break drops city pressure to zero while a garden hose is left submerged in a bucket of fertilizer. Contaminated water is drawn back into the potable system. What is this type of backflow called?
a.Backpressure from a booster pump
b.Water hammer
c.Thermal expansion
d.Backsiphonage caused by negative or reduced supply pressure
Explanation
Backsiphonage occurs when a drop in supply pressure (from a main break, firefighting, or heavy demand) creates a vacuum that siphons contaminated water back through a submerged connection into the potable system. It differs from backpressure, where a downstream pump or pressurized source pushes water backward. A simple hose bibb vacuum breaker prevents backsiphonage at outdoor faucets.
Law Reference: California Plumbing Code §603Practice all 360 questions free — no signup required.
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