What device is installed to prevent water from flowing backward into the incoming supply?

A backflow prevention device is critical in plumbing and water systems to ensure that water flows in the designated direction and does not reverse back into the supply lines. This device helps protect the water supply from contamination by preventing potentially polluted water from flowing back into the main supply.

Backflow can occur due to changes in pressure within the system, for instance, when there is a sudden drop in pressure or during certain maintenance operations. The backflow prevention device works by utilizing mechanical features, such as valves, that close and prevent reverse flow when a backflow condition is detected.

In many applications, especially in industrial and commercial settings, the installation of backflow prevention devices is mandated by laws and regulations to maintain public health standards and ensure safe drinking water supply. The other devices mentioned, while important in their own contexts—such as water softeners for reducing hardness in water, flow regulators for controlling flow rates, and spill containment units for managing hazardous substances—do not specifically address the concern of preventing backflow into the incoming supply.