PERFORATED BLOCK FOR UNDERDRAIN HAVING UPPER PART WALL AS CONCAVO-CONVEX RECOVERY WATER COLLECTING STRUCTURE

摘要

PURPOSE: To provide a perforated block for underdrain, which is able to evenly distribute air and water when backwashing a rapid filter by improving a structure of the perforated block. CONSTITUTION: The perforated block (10) comprising a closed bottom, outer side walls (12) that are formed on both sides of the bottom, an upper part wall (13) that is formed between upper ends of the outer side walls, inner side walls that are inclined from both ends of the bottom to a center lower part of the upper part wall and perforated holes that are formed at the inner side walls and the upper part wall to allow water and air to be flown in or out is characterized in that the upper part wall has a concavo-convex surface and perforated holes (16a,16b) for recovering or supplying filtering water and backwash water are formed on a concave portion (13a) and a convex portion (13b), respectively.