How is backflow defined in a potable water distribution system?

Backflow in a potable water distribution system is specifically defined as the flow of liquids in the piping for a potable water system in reverse. This phenomenon typically occurs when there is a drop in water pressure in the distribution system, allowing contaminated water to flow back into the clean drinking water supply.

Understanding backflow is critical for ensuring public health and safety, as it can introduce harmful pollutants or contaminants into potable water. Backflow can be caused by various factors, such as water main breaks, plumbing malfunctions, or even a sudden increase in demand on the water system. Therefore, systems are usually equipped with backflow prevention devices to mitigate these risks and maintain the integrity of the potable water supply.

Option addressing the flow of liquids in the intended direction describes normal operation within the system, while the flow of solid waste materials is irrelevant to potable water systems. The flow of air in ventilation systems pertains to entirely different systems and functions.