I change about 150 gals A week for my 480 I use A transfer pump hooked up to A 1 inch hose it empties it in less than 7 minutes.
I then use A variable pump hooked up to A 1 inch hose I put A 5 gallon bucket in the bath tub I run the bath water at the max into the bucket with the pump in it
Total time between empting and filling less than 35 minutes