The first couple of times I added DE to my sand filter, the same thing happened -- my pressure shot up too far. I was expecting the pressure rise to happen quickly and when it didn't, I added a little more and then a few minutes later it was way too high. It takes a couple of tries to figure out how your filter is going to react. As Janet said, take it slow and wait a bit before you add more. If you overshoot the 1psi rise, do a quick backwash and try again. Eventually you learn how much is required for your particular setup.