The TETRA LP Block dual parallel lateral underdrains offer low head loss, equal distribution of backwash air/water and easy installation either as a retrofit or for new filter underdrain applications. TETRA LP Blocks feature the patented GroutGrip and Anchor-Rite designs. The GroutGrip design increases resistance to uplift from the filter floor, and the Anchor-Rite design securely fastens the block to the floor.