Opened pool about a month ago and the water still have lots of small particles especially near return lines. I also see lots of sand (probably DE) on the floor. I decided to open the filter (never done this by myself before) and found that plastic on top of the grid has some cracks. I assume this is the top manifold and I believe the cause of my problem. I found replacement part, but canít figure out how to do you replace it. Do I have to unscrew two plastic hex nuts and lift the grid out? Does anyone have instructions how to do it?