Quote Originally Posted by Krizoid View Post
Will my PH stop drifting up to 8+ when the alkalinity is lower?
Yes.


Lastly I have had a tough time getting a good answer on why I need to maintain a pool at PH <7.8.
Chlorine becomes less active as the pH goes up; water balance (pH + calcium hardness + alkalinity) becomes harder to manage; you'll have to buy a pH meter to manage things.

That's a very, very brief explanation that over-simplifies things, but is correct practically speaking.

If you want more, I'll put you in touch with all the work Chem_Geek has done -- but understand you don't need to know, to do your pool well.