Support Gravel

Support gravel, also known as support media or underdrain gravel, is a carefully sized and graded aggregate material placed in the underdrain system of industrial filters. It serves multiple critical functions: providing a stable foundation for filter media (such as sand or anthracite), preventing fine media particles from entering and clogging the underdrain laterals, promoting uniform water or fluid distribution across the filter bed, and facilitating efficient backwashing during filter regeneration cycles. The material is characterized by its particle size distribution, hardness, and chemical inertness to withstand operational conditions.

Support gravel operates on the principle of graded filtration and structural support. It is layered with progressively smaller particle sizes from bottom to top, creating a stable transition zone between the coarse underdrain laterals and the fine filter media. This arrangement prevents media migration into the underdrain, ensures even fluid distribution during filtration and backwashing by reducing channeling, and maintains bed integrity under hydraulic loads. The gravel's porosity allows fluid passage while its mechanical strength supports the overlying media.