I have two skimmers in my pool. When I remove the basket from the main skimmer (the one I use to vacuum the pool) I see two pipe openings. When I put my hand down into the lower one I can feel the suction and it looks to be clear. When I put my fingers into the second I feel sand/grit. I've never noticed this before and was wondering if that sand/grit is meant to be there (to filter) or is something that needs to be cleaned out. Thanks.