Which device is specifically designed to prevent water from flowing back into the supply line?

The device designed specifically to prevent water from flowing back into the supply line is the check valve. This valve allows water to flow in one direction only, effectively stopping any potential backflow that could occur due to changes in pressure. Backflow can lead to contamination of the clean water supply, so the check valve plays a critical role in maintaining water quality and system integrity.

When water pressure is present in the right direction, the check valve opens and allows water to flow through. However, if there is a drop in pressure or a reversal of flow, the valve closes, thus preventing any reverse movement of water into the supply line. This mechanism is essential in irrigation systems to ensure that fertilizers, pesticides, or other contaminants do not re-enter the potable water supply.

In contrast, devices like solenoids, filters, and manifolds serve different functions within an irrigation system. Solenoids control the opening and closing of valves, filters remove particles from the water to maintain quality, and manifolds distribute water to different parts of the irrigation system. Each serves a necessary role, but none are specifically designed for the critical backflow prevention feature that a check valve provides.