Filter underdrain system for backwash flow and method for measuring same

摘要

A filter underdrain system and a method for measuring the water flow through the underdrain filter system. The apparatus includes panel members assembled to form a perforate grid on the filter base structure of an underdrain block. The panels are generally rectangular and have an upper and lower surface. Multiple apertures are provided in the panel member. The number and/or size of the apertures are dimensioned to prevent the egress of filter media and to obtain substantially uniform backwash flow in the underdrain thereby reducing or eliminating water maldistribution.