My daughter is having 8 friends over, and wants to have a night pool party. The pool is still open, but we aren't really using it because it is so cold (65-70). She wants me to jack the heat to 90 so they can float around at night like a hot tub. I roughly calculated that it costs $3/hour to run the heater, and it raises the temp 2 deg/hr, so it would cost approx $50 for the day of heat. High, but not extreme divided by so many kids.
Is there a problem heating that hot (besides the expense) in october?