Draining with a cartridge filter

[waterbear]

most cartridge filters have a drain plug or a hose bib on the bottom to drain water out of the filter. You could open that up and turn on the pump to drain water out of the pool. If the filter is below the level of the pool you might not even need to turn on the pump.

[imfignewton]

Add a threeway valve somewhere after the discharge side of the pump and add some PVC pipe or a backwash hose.