How much borax to raise PH?

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

I just went through something very similar. Opened pool to low PH (6.8 or lower), TA was OK, vinyl pool. I did BOTH, aerated and added borax. Why? My PH was low enough that I was worried that the vinyl liner might wrinkle as the pool warmed. So I started aerating (which did bring the PH up, but somewhat slowly) and added a large box of borax. After a few days, everything was fine.

The borax was an insurance policy, it made me feel better to get the PH up fairly quickly.

Sounds right to me. I think you only add Borax when your TA is correct and you need to raise your PH a little to get it correct. Great questions. I am still learning also.

I like to think of the acid/aeration cycle as a 'ratchet' type of mechanism for adjusting TA.

You crank the TA down by reducing it and the PH with acid, then you 'reset the crank' by aerating to raise the PH back up leaving the TA where it is.

Repeat as necessary.

...but I tend to be a simple type of guy. :)

I know everyone says if I follow the "how to lower your alkalinity" thread exactly, it WILL work. HOWEVER, mine will not budge below 160. It went from 280 to 160 using this method, but no matter how much muriatic acid I add now, it won't budge. I'm aerating with a fountain that sprays out of my return and really seems to be bubbling and rippling the water. Also, we had a good rain last night too. Still not moving down. My PH went up from 6.8 to 7.5 with Borax. It went back down to 7.2 with the acid, and now back up to 7.5 with the aeration. I will add more acid to lower it again (no lower than 7.0 I know), and keep aerating I guess. I still don't understand why the ALK won't budge any further than the initial 120 drop from 280. If the water wasn't 64 degrees, I'd let my kids get in there to further aerate.

I wouldn't be worried about it at 160. I lived with mine at 200-ish for some time before winter rain dilution dropped it. As long as you don't have high calcium hardness and you aren't experiencing cloudy water, leave it be. I always pushed my pH down to 7.0 whenever I had to add acid, and it seemed I'd gain a little every time, but I didn't work at it.

Ben always said that pools find a value that they 'like', and you're best bet is to learn what your pool likes and manage around that.
160 ain't too bad.

Ok, these were my numbers from this morning using the HTH 6-way test kit from WalMart:

TC - 4
PH - 7.4
ALK - 140 (it actually came down 20 more and now I'm DONE with it! LOL)
TH - didn't work

I know we have hard water (from a well, and no softener). When I filled pool water to the appropriate line and added 5 drops of hardness indicator, the water turned a light yellowish/tan instead of red like it said. Then I was supposed to add the titrant drop by drop until the "red" water turned blue. I kept adding (just to see what color my yellow would turn) and nothing changed. If anything it looked a little more clear colored. Does this mean my hardness is waaaaaaaaaaaaay up there, or that my chemicals need replaced maybe? I bought the kit last year in July. Not sure how long they are "good" for. Any ideas? Last year my hardness was 480 (yikes) but we have a vinyl pool and no problems with cloudy water so I didn't mess with it.

Dena
15x30 Esther Williams AGP 10,000ish gallons