I'm opening my pool again this year and have gotten water chemistry correct then shocked. The pool was very green to start and no free chlorine. After shocking it seems like I have to backwash my filter every 2 hours. I cleaned the grids and it didn't really improve much. I'm averaging 2-4 hours before it pressures up. This happened last year too but eventually after enough backwashes the water cleared up and didn't have to backwash again until the end of the season. I just am going through DE like mad and wondered if this is normal or not. Any advice would be appreciated. I replaced the grids a year or two ago.