ADEQ Water Distribution Grade 1 Certification Practice Exam

When backsiphonage occurs, the pressure in the service line falls below the normal operating pressure of the public water system. That drop creates a suction effect, pulling water from customer piping back into the distribution system and potentially introducing contaminants. So the service side shows reduced pressure, often even dipping below atmospheric in the worst cases. Increased or normal pressure doesn’t drive the siphoning, and while pressures can fluctuate, the characteristic feature of backsiphonage is a reduced pressure on the supply side, which is why backflow prevention is essential.