How much borax to raise PH?

[chem geek]

After you get your TA where you want it (and after you are through with the TA lowering procedure), then if your pH gets too low at some point you can use Borax to raise it. However, unless you use an acidic source of chlorine (e.g. Trichlor) or a non-chlorine shock (e.g. potassium monopersulfate) or add CYA directly, then there shouldn't be anything in your pool making your pH go down.

The natural tendency for pool water is to go up in pH because it's been intentionally over-carbonated (like a tasty beverage!) and the outgassing of the excess carbon dioxide will tend to make the pH rise. Of course, when you stop the aeration, this tendency will be lessened, hopefully to the point where your pH will be stable. A lower TA will help this stability because carbon dioxide outgassing is faster at low pH, high TA, and with more aeration (so conversely, pH is more stable at higher pH, lower TA, and with less aeration).

Eventually, the slow outgassing of carbon dioxide and the small amount of acid you may add over time to maintain pH will result in a slow lowering of TA at which point you can increase it, but with properly adjusted water parameters, that day may never come. Every pool has a sweet spot or balance and after you've got your TA lowered, you'll learn what that is for your pool.

Richard