High filter pressure

[PopPop18]

I have a problem with high filter pressure. I just opened my pool and the pressure went up to 20 psi after about 1 1/2 hours. I bumped it down and it went back down to 10 psi and after about 1 1/2 hours it went back up to 20. I flushed the tank, put in new DE powder and the same thing happened again. I do have good flow through the returns until the pressure rises. Any idea's of what may be causing this? My pressure gauge is new, my filter is 2 years old. Any help would be greatly appreciated!!!

[howzball]

How long since you opened the filter and cleaned the grids?

Maybe they're caked up with too much old DE, not all of the DE gets removed during backwashing. Ever so often, it's a good idea to split open a DE filter and hose it down to wash all the stuck on gunk out of it.