Up here in New Hampshire closing the pool includes draining the filter completely so it won't freeze. I have a Hayward DE filter and I usually backwash it, then open it up and remove and clean the elements as well as draining it.
This year there seemed to be a lot of DE remaining in it. Like an inch of it caked on the outside of each element.
The filter worked fine all summer. It always starts at 15 PSI of pressure and I backwash when it has risen 10 PSI. I always backwash it until the water runs clear, then cycle it back to filter and back to backwash a few times, then add the requisite 6 lbs of DE through the skimmer. Frankly, I sometimes wonder why I don't seem to get a lot of DE collecting on the ground where the outflow is, but the filter works, so...
So why was there so much DE remaining when I opened it? Am I not backwashing it long enough? Should I see a lot of DE on the ground when I backwash? Have I been putting too much DE in each time (rated for 6 lbs)? Is it normal to have a lot of DE caked on the elements when you open it up, even after backwashing?