What is the maximum amount of gravel required for Wheeler underdrains?

The maximum amount of gravel required for Wheeler underdrains is 12 inches. This specification is critical because it ensures that the drainage system functions effectively by providing sufficient space for water to flow and preventing clogging. Proper gravel depth allows for optimal filtration and drainage capabilities, which are essential in managing surface water and maintaining the integrity of the underdrain system. Having the correct depth also contributes to the longevity and reliability of the installation, minimizing the risk of water pooling or saturation in adjacent areas.

The other options specify lesser depths which would likely compromise the system's effectiveness in redirecting excess water and could lead to drainage issues. Ensuring that the gravel meets the 12-inch requirement can help mitigate these potential problems.