I just want to say thanks again for all your help. I added the Borax about 1/4 of the box and by the next day the water was crystal clear. and now that it is crystal clear I notice sand or DE on the floor of the pool. The last time I took the filter apart I inspected the fingers pretty well I thought and everything looked perfect. I did notice that i was missing a screw and nut on the rubber connecting it to the cover. Could this one missing screw be enough to allow some DE through or is there something else I should be checking?