Welcome to our forum.
Just turned the heat on Saturday AM as well. Overnight temps have been in the 40's and should dip into the high 30's as the week progresses. Also just drained and refilled the hot tub on Saturday but haven't had a chance to soakin the new water yet due to being too damn busy. However, I am looking forward to soaking tonite after TKD class.
When you say you turned up the heat do you normally keep it down if you are not using it? What do you keep it at?