What is the main function of a backflow preventer in a water distribution system?

The main function of a backflow preventer in a water distribution system is to prevent the reverse flow of contaminated water into the potable water supply. This device is crucial in maintaining the safety and quality of drinking water. Without a backflow preventer, there is a risk that water from non-potable sources, such as irrigation systems or industrial processes, could be siphoned back into the clean water lines during events such as a drop in water pressure or system malfunctions.

By using a backflow preventer, water utilities ensure that the integrity of the potable water supply is protected from potential contaminants, thereby safeguarding public health. These devices operate by creating a physical barrier that prevents backflow and often include features like check valves that automatically close to block reverse flow.

The other options, while related to water distribution, do not directly address the primary concern of protecting potable water quality from contamination, which is the essential reason for implementing backflow prevention measures.