New here - hoping for some help.

Have a 20K gallon in ground pool just opened. Pressure last year at sand filter was about 12 to 15 PSI. It is now only 3, barely able to vacuum. Tried a drain king to clean out skimmer line to no avail. A little air in pump basket area, not much. Pump impeller looks clean.

Here is the kicker - I seem to get more flow at the skimmer when in waste mode than in filter. Don't get a pressure reading unfortunately when in waste or recirc mode. Any ideas would be much appreciated.