The dealer printed out a list of chems that i need to add to the tub after initial fill (485gal tub). The first one is Total Alk Increaser. The instructions say to divide the total dose (1 cup) into 3 separate applications and wait an hour between each application.
I'm guessing he tested your water.
It's always best to add little doses every couple of hours opposed to large doses more frequently. I wait till the next day before adding a second dose to my water most of the time.
TA increaser is Sodium Bicarbonate(Baking Soda)
Should I run the jets for the full hour between applications or is 20min good enough?
20 minutes is fine.
Should I leave the cover open fot the full hour or can i close it up between applications?
When just adding BS, close her down after the 20 minutes. Now if you were adding a super shock dose of dichlor, you might want to wait an hour.
Is it ok to wait 24 hours before adding chlorine or some other sanitizer
I'm not sure on this one but if I had to guess I'd say probably not a good idea.