Lid for an underdrain block

摘要

A lid for an underdrain block that has a top surface defining an opening for receiving fill material. The top surface forms a ridge circumscribing the opening, the lid comprising a top, a bottom and a peripheral edge, the peripheral edge comprising a rim adapted to interlock with the ridge. The ridge of the underdrain block can have a flange perpendicular to the top surface and the rim on the lid is adapted to tightly fit over the flange so that the rim interlocks with the flange. Alternatively, the underdrain block for a filter system comprises a hollow plastic housing comprising a top wall that defines an opening for receiving the fill material. The top wall forms a ridge surrounding the opening and the lid seals the opening in the top wall. The lid comprises a peripheral edge that forms a u-shaped rim. The u-shaped rim has a locking means to tightly fit over the ridge so that the rim interlocks with the ridge so as to seal the opening.