An indirect cross connection allows what type of backflow to occur?

An indirect cross connection primarily allows for backsiphonage to occur. Backsiphonage is a specific type of backflow that happens when there is a negative pressure in the supply piping system, which can create a vacuum effect that draws contaminated water into the system from a secondary source.

In scenarios involving indirect cross connections, the potential exists for contaminated water to flow into the potable water supply if there is a drop in pressure, such as during a main water line break or when water is withdrawn from the system (for example, through a fire hydrant or during a high demand situation). The absence of direct physical connection between the two water systems allows for this type of flow to occur under conditions that lead to backsiphonage.

Understanding this concept is essential for managing backflow risks effectively and ensuring safe drinking water supplies, thereby emphasizing the importance of monitoring indirect cross connections in plumbing systems.