15x48? About 4,400 gallons?

Unless you have a faithful neighbor, or really expensive water, it might be better to use your pool water to water your plants, and refill on return. Leave at least 6" in the bottom, and add some polyquat. Then pump the remainder out when you return and start over.

A pump like this is what you need (and will need this fall):
Superior Pump 91250 1/4 HP Thermoplastic Submersible Utility Pump

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