What Is Backflow Prevention—and Why the Law

Backflow prevention refers to measures designed to keep water from moving in the wrong direction—specifically, preventing contaminated or non-potable water from flowing back into a potable (drinking) water system.

Under normal conditions, water moves from the utility’s mains into homes and businesses. But certain pressure changes can reverse that flow, creating a risk that pollutants could enter the drinking-water supply.

Backflow can occur during events such as firefighting, major water main breaks, or malfunctioning water pressure equipment. It may also be triggered by connected systems that carry chemicals, wastewater, or other materials—especially when those connections are not properly protected.