My pool pro says I need to drain half the water in my pool and refill with new water. Half the water is about 7,500 gallons. I don't want to run the submersible pump overnight --- I'd rather be awake in case some problem occurs -- so can I do part of the draining on one day, and then do the rest of the draining the next day? Will that harm anything? So I'd be draining approx 3,750 gallons one day, and another 3,750 gallons the next day. Daytime highs here about 85 degrees, dry, am draining into my sewer lateral. Thanks in advance.