Aylad, thanks for the reply. I measured 15ppm free chlorine last night at about 9pm and I just checked it again this morning at 7:30am and got 14ppm free chlorine. I don't see sand blowing back into the pool, I do see that pressure drops after I backwash, I do run the filter through a rinse cycle after backwashing until the sight glass is clear and my filter pressure does rise. It rose pretty quickly at first, but now it's rising more slowly. I purchased some EcoKlean cellulose based DE substitute so is that OK in place of the DE? Is it possible that my 1.5 HP pump is pushing too much water through the filter? (just one of my thoughts).

By the way, I'm in NH and the water is still pretty darn cold, if that makes any difference.

Thanks,
JP