Quote Originally Posted by sox6035 View Post
Chlorine: total- 9.5 Free-7.8
Alkalinity: total- 122 Free-99
CYA: 76

You've already been given most of the info you need. But I wanted to point out that your test results tell me you are using a totally bogus computer test method of some sort or another.

Why bogus?

Very simple.

The best available field test method for CYA can barely distinguish between 70 ppm and 80 ppm, and can only do so reliably using a precision (= very expensive!) spectrophotometer. The digital strip readers commonly used by pool dealers have displayed resolutions of 1 ppm or even 0.1 ppm . . . but an accuracy of less than +/- 25 ppm. We have *often* seen CYA test errors on dealer pool test results of 30 - 50 ppm!

Please note: the digital units have an actual error value that is 20 to 200x times LARGER than the apparent resolution (and implied accuracy) shown on these god-forsaken devices!

However, because the only way pool owners come up with results like CYA = 76 is one of these digital units, we can recognize the bogus results.

Here's what your test results SHOULD be, if 'truth in marketing' were enforced:
pH: nominal value => 8.4; range of likely actual values => 8.0 - 10.5
Total chlorine: nominal value => 9.5 ppm; range of likely actual values => 6 - 12 ppm
Free chlorine: nominal value => 7.8ppm; range of likely actual values => 4 - 10 ppm
Total alkalinity: nominal value => 122 ppm; range of likely actual values => 90 - 150 ppm
Adjusted* (not: "free") alkalinity: nominal value => 99 ppm; range of likely actual values => 60 - 140 ppm
CYA: nominal value => 76 ppm; range of likely actual values => 30 - 120 ppm
* adjustment based on inaccurate CYA measurement!

Accurate measurement of CYA is possible . . . in a sophisticated lab. Here's the analysis process for CYA in the 0 - 5 ppm range with a detection limit of 0.1ppm:
Assay methodology
The assay methodology for measuring cyanuric acid in pool water samples and urine specimens have been described previously by Cantu´ et al. (2001a,b).

Briefly, the pool water samples were filtered, using an activated cellulose filtration disk, followed by dilution of a suitable aliquot with deionized-distilled water. Samples were then refrigerated at 48C in an amber colored plastic storage bottle for no more than one week before analysis. A 25 ml aliquot of the sample was directly injected into a porous graphitic carbon column for reversed phase high performance liquid chromato-graphic analysis (RP-HPLC). Separation of cyanuric acid was achieved using isocratic elution chromatography with a mobile phase of 95% 50mM phosphate buffer (pH 9.1) and 5% methanol (% v/v) followed by UV detection at 213 nm. The procedure was linear in the range of 1–5mg/l with a detection limit of 0.1mg/l. Cyanuric acid was quantified using an external calibration curve. To avoid biological and chemical degradation, the 24 hour urine sample was immediately preserved after collection by the addition of 1ml of a reagent composed of 10% (v/v) perchloric acid and 1% (w/v) metaphosphoric acid. The urine was cleaned by initially centrifuging 1.5ml of the preserved sample. Next, 1ml of the supernatant was loaded onto 3 previously conditioned, stacked, solid phase extraction cartridges. The filtered urine sample was eluted from the cartridges using 4ml of a 0.05M hydrochloric acid solution. Subsequently, 2.5ml of dichloromethane was added to 1.5ml of the filtered urine, the mixture was vortexed, and the phases were allowed to separate. A 450 ml aliquot of the aqueous phase was then transferred to an HPLC auto-sampler vial and stored at 48C. Just prior to analysis, the pH of the aqueous phase was adjusted with sodium hydroxide and the sample immediately injected into a porous graphitic column as indicated above for the pool water samples.
Please note, this method requires use of a HPLC (High Pressure Liquid Chromatograph). Here's a Google Shopping link, to give you an idea of why your neighborhood pool dealer is NOT likely to be using an HPCL:
https://www.google.com/search?q=hplc

In the wake of melamine & cynauric acid doping of pet foods and infant formula by Chinese export manufacturers, the FDA has approved an even more elaborate, accurate -- and complex -- methods of analysis:
http://www.fda.gov/Food/FoodScienceR.../ucm071673.htm

Meanwhile, we'll continue to recommend the use of the turbidimetric (cloudy water) method found in the Taylor K2006 testkit, which provides adequate accuracy (+/- 10-20 ppm) for pool operations.