What is the primary purpose of a backflow preventer?

The primary purpose of a backflow preventer is to ensure that water flows in one direction. This device is essential for maintaining the integrity of a potable water supply by preventing contaminated water from flowing back into the clean water supply. Backflow can occur due to changes in pressure within the plumbing system, such as during a sudden drop in water pressure caused by breaks in water mains or other disruptions. A backflow preventer is designed to withstand these pressure changes, ensuring that any contaminated water does not reverse flow into the drinking water system, thereby protecting public health and safety.

Options that suggest allowing water to flow in multiple directions, increasing water pressure, or filtering out contaminants do not accurately describe the function of a backflow preventer. The device is strictly concerned with maintaining directional flow, not altering pressure levels or performing filtration tasks.