In backflow prevention, what does "backsiphonage" refer to?

In backflow prevention, backsiphonage specifically refers to a situation where a drop in pressure in the supply system causes water to flow backward through the plumbing system. This can occur when there is a negative pressure or vacuum created in the distribution system, which can happen, for example, during maintenance work or if there is a sudden increase in demand downstream.

When backsiphonage occurs, contaminants from the surrounding environment can inadvertently be drawn into the potable water supply. Understanding this process is crucial for implementing effective backflow prevention measures to ensure potable water remains free from contamination.

While the concept of reverse water flow is related to backsiphonage, what distinguishes it is the necessity of a pressure drop that causes this reversal, which makes the selected definition accurate. Other forms of backflow, such as backpressure, may involve different mechanisms that do not necessarily rely on a pressure drop.