Thanks for the information you posted.
I am having a problem with my Hayward DE filter (36sqf). It can not hold earth at all. When cleaned it up, put filter grid back, close the cover, start pump, put earth in skimmer, all earth returned back to the pool, and make it so cloudy. I did this job for so many years, never have this problem. But since several month ago after used Phos Free. Phos free killed my filter grid, so I replaced old with new filter grids. Then problem came out.
Could some one shed light on this? I reaaly appreciate.