Hi. I found the site while researching how to get or pool back in shape. The pool servicer wanted to replace our sand filter with a filter for $2,450 (next day since we were trying to have the pool ready for a party). Anyway, we didn't; we replaced the multi-port valve, standpipe, laterals and sand, depending on much info read here. We have shocked the pool and the numbers are coming around. So, thanks so far!