COMBINATION OF CAP AND UNDERDRAIN BLOCK OR UNDERDRAIN DISTRIBUTOR IN FILTER

摘要

PURPOSE: To eliminate necessity of supporting gravel in a filter bed and to maximize distribution between backwash gas and backwash water. ;CONSTITUTION: An improved cap 10 for underdrains in gravity filters has a top surface 12 and a bottom surface 14 with a plurality of tapered screen members 20 defining slots 22 on the top surface. The slots provide communication with the filter bed without a passage of fine grain filter media therethrough. The screen members 20 are inclined with respect to horizontal to define a plurality of raised portions 24 on the top surface and each raised portion defines a distribution chamber 26 above the orifices 18 in a distributor 16. The cap 10 may be included in a filter underdrain block having a plurality of ribs 36 and the orifices 18 on a top wall of the distributor.;COPYRIGHT: (C)1994,JPO