What effect does a negative pressure have on a water distribution system?

A negative pressure in a water distribution system can lead to backsiphonage, which is a significant concern in water supply systems. When negative pressure occurs, it can create a vacuum effect that draws water back from service connections or open systems into the potable water supply. This can introduce contaminants from the environment or from other sources, making the water unsafe for consumption.

The risk of backsiphonage emphasizes the importance of maintaining positive pressure in the distribution system to ensure that water flows outward from the distribution mains into service lines, rather than being drawn back. This is crucial in preventing contamination and protecting public health.

On the other hand, options like enhancing flow rates, purifying water, or maintaining chlorine levels do not accurately represent the consequences of negative pressure, as those would typically require a stable or positive pressure environment.