Well, for my filter it seems it takes 2 1/2 cups of DE to bring it up 1 PSI. I'll let that go for a few days and see how it works. Sadly, I now have a 25lb bag of DE, so that should last me about 100 years. After I told the rep about what I was doing at the pool store he predicted doom, fire, flooding, and the splitting of the earth by putting DE into my sand filter.

It seems like EVERY tip I've gleaned from this site and it's sister site, the "local pool pros" absolutely hate.