I have been vacuuming my pool since we opened it in early May to try and get the bottom of the pool clean. There is sediment on the bottom that collects on the wrinkles and small divots. The chemistry is fine. I just changed the sand (yes I used pool sand) in the filter last year. I bought a new cover/handle assembly for the multiport valve because I thought the gasket was worn, it was, but I vacuumed this morning after the assembly was changed and now just 2.5 hours after I vacuumed, the same light brown "dirt" is beginning to show up again in all the same places. HELP!! What the heck is going on?? The water is crystal clear. No algae and no dead algae. In fact, I've only opened up the pool once in the last nine years and had as clean water as this year. I vacuum slowly and the dirt does go into the vacuum head and to the filter. For about 30 minutes the bottom looked great.