What is the purpose of anti-drain valves in an irrigation system?

The purpose of anti-drain valves in an irrigation system is primarily to prevent low head drainage. These valves are designed to hold water in the irrigation lines, preventing it from draining back into the water source when the system is turned off. When the irrigation system is not actively watering, gravity can cause water in the lines to flow back down, which can lead to dry spots in the area being irrigated or reduce the effectiveness of future irrigation cycles. By keeping water in the lines, anti-drain valves ensure that the system is ready for immediate use and helps maintain a consistent distribution of water to the plants.

In contrast, other options do not align with the function of an anti-drain valve. While pressure regulation and maintaining water flow are essential aspects of irrigation systems, they are managed by different types of valves and components, not specifically by anti-drain valves.