To cut the Gordian Knot there's a very simple way to steadily add acid to your pool, assuming your CYA isn't too high, or is even low:

Just load a floating chlorine dispenser with Tri-Chlor tabs.

Tri-Chlor is VERY acidic and will lower your pH or fight the raising of it by your SWCG. It's an effective and far cheaper solution. I've come home from vacations with my pH TOO low from the floaters (oops!).