Too much borax, now ph +8.0

[AnnaK]

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.

[CarlD]

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

[madwil]

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?

[chem geek]

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.