[QUOTE=ubalr1]Lastest water test at local pool store:
CYA 168
TC 0.6
FC 0.6
pH 6.9
TA 126
Adj TA 76
TH 527
TDS 2100
20,000 gal, in-ground gunite
Cartridge filter

Ahhh! This is confusing. What is the defference between Total Alkalinity (TA) and Adjusted TA. What I forgot to post originally was the Adj. TA as calculated? by the pool store. Adj. TA was 76. Which should I really be using to make adjustments.

I found this formula online:

Adjusted TA = TA - (Stabilizer X Stabilizer Factor)
with
Total Alkalinity Adjustment Factors:

PH____Cyanuric Acid Factor
7.0____0.22
7.2____0.26
7.4____0.30
7.5____0.32
7.6____0.33
7.8____0.35
8.0____0.36

Following this formula (and extrapolating for my pH since it's just off this chart)
I get an Adj TA of 90.72 (not 76 like the pool store)

Adj TA = 126- (168*.21) = 90.72

We're heading back to the pool store for another test since we added 12# of sodium hydrogen carbonate yesterday. Our test kit fo TA indicates not much change in TA.