What causes backsiphonage in a water system?

Backsiphonage in a water system occurs when there is a negative or below atmospheric pressure within the system. This situation allows contaminated water from another source to be drawn back into the potable water supply, creating a potential health hazard. When pressure drops within the water distribution system—often due to a water main break, excessive water withdrawal, or fire fighting— it creates a vacuum effect. This low pressure can siphon water from lower elevation points or connected systems, leading to a backflow of potentially unsafe water.

The other factors, while they can affect water distribution, do not directly create backsiphonage. For example, excessive water pressure can lead to other issues like leaks or bursts but does not create the conditions necessary for backsiphonage to occur. Similarly, contamination of the water source is a result of backsiphonage rather than the cause and refers to the consequence of allowing backflow to occur. Malfunctioning pumps could affect system pressure but are not specifically linked to the phenomenon of backsiphonage as negative pressures are the primary cause. Understanding these dynamics helps in designing and maintaining systems that prevent backflow and ensure water safety.