My daughter is having a birthday party this Saturday. The temperatures this week are supposed to be in the 70's (highest 79 on Thursday) with Saturday being 63 We are going to heat our 18,850 gallon pool for the first time for her party. We do not have a solar cover. How long with a 400,000 btu heater will it take to heat the pool from 60 (what it currently is, although I hope it is warmer after a week in the 70's) to 82? I want to make sure we get the pool warm enough to enjoy but don't want to heat it longer than I really need to. I have also thought about buying a liquid solar cover just for the party to keep the heat in as I am heating it up but I have read bad reviews.
Thanks in advance!