Too much borax, now ph +8.0

Hello all, my pool finally cleared up. But, I over shot my ph levels. It was about 7.0, I added a box of Borax and now it's 8.0+. My pool is 12k gallons. How can I use the "shot glass method" to test PH? Here are my numbers.

FC 30
TC 30
PH 8.0 or higher
CYA 95
TA 80

What should I do? What will happen if I leave it? What is the highest, safe CL level?

BTW, Last year you may remember my ph was super low, off the chart. I added about 10 boxes of borax to get it up to the 7 range. Someone asked how this happened, I had no clue. Last night I started thinking about how it got so low and came up with an answer. I had a brick patio installed. While the men were working, a huge amount of brick dust ended up in pool. I ran filter and it cleared up. I think that's want brought my ph so low. Any thoughts?

the higher pH is not good, you need some acid to bring it down- slowly! I'd add maybe a cup at a time, retest in an hour (with pump on!) and add little more (or next day) til you got it down to 7.6 or so...
don't think there's a shotglass method for pH, because the scale is logarithmic
With your CYA level, FC of 25-30 is shock level and is safe

ultimately, you'll raise your borates level and that's an algae inhibitor, so don't worry. Just keep adding acid to bring it down. A cup at a time is fine.
Many people add lots of Borax and then Muriatic Acid to bring it down to try to reach a borate level of 50ppm.

Carl

With an FC of 30 your pH readings are likely unreliable. You might try diluting your pool water to an FC below 10 and retest the pH before you attempt any changes.

Not a bad idea, Anna!
Use Distilled water, not tap water because tap water may have chlorine in it and also has pH issues. Steam distilled should be pH neutral.

Carl

pH is measured on a log scale, so dilution method is not direct; meaning 2-1 dilution doesn't result in 2-1 scale reading. Also, the distilled may not be 7.0 pH, so would throw it off.
I remember in chemistry doing some pH calcs for mixing different pH, but don't remember how- maybe chemgeek can give some pointers?

I think the suggestion for dilution was to get the FC level down so it won't interfere with the pH test. So long as you dilute with UNBUFFERED water, such as distilled water, then you should be OK since the dilution will have no measurable effect on the pH (it has a very small effect, but way less than the 0.1 units measurable on the pH test). However, if you use buffered water for the dilution, then all bets are off and you'll be affecting the pH significantly.

Basically, when you dilute buffered water with unbuffered and neutral pH water, you cut ALL concentrations down equally, but since the pH of buffered water is mostly related to the relative ratios of the carbonate buffer system, the net pH result is hardly changed at all.