What is the purpose of a drain valve in an irrigation system?

The function of a drain valve in an irrigation system is primarily to remove water from the system after it has operated. This is essential for several reasons, including allowing for maintenance, preventing potential freezing damage in cold weather, and ensuring that the system does not retain water that could become stagnant. By effectively draining water from the lines, the drain valve helps maintain optimal performance and longevity of the entire irrigation system.

In terms of other options, while controlling water pressure and preventing water waste are important aspects of irrigation management, they do not pertain directly to the specific function of the drain valve. Similarly, the application of water to plants is handled through other components of the irrigation system, such as emitters or sprinklers, rather than by the drain valve itself. Thus, the primary and correct purpose of a drain valve is accurately captured by its role in draining water from a line after operation.