my pool guy wants to do this tomorrow if pH is too high and alkalinity is below 80. i've never done this- always wait 24 hours. is this ok?
That is a little counter productive. Do you do your own testing? Can you post a full set of numbers?
The 80 to 120 rule is based on incorrect information. It is not a useful guideline to follow. I would suggest that you base the TA on how the ph moves. If the ph rises, the TA is probably too high. If the ph drops, the TA is probably too low. When the ph remains stable, the TA is just right.