CYA in a sock

[polyvue]

Precursor: http://www.poolforum.com/pf2/showthr...4969#post64969

CYA Application Experiment June 29, 2010

Though I was fully prepared to retract my rash assessment before doing this experiment (and may still have to if my pool turns out to be 9 or 10K gallons instead of the 14K gallons I believe it is) it appears that I have been conservative in my estimation that CYA dosing shows up in testing in a few hours instead of a few days. I think preliminary testing shows that there is nearly full dissolution in less than 60 minutes.

Procedure

Using the Pool Calculator, 37 ounces (wt) of cyanuric acid (stabilizer) should increase CYA by 20 PPM and effect a reduction in pH of .37

Predict CYA 50 PPM and pH 7.33

I weighed the CYA granules on a postal scale and split into two batches, making a one gallon slurry from each and adding one right after the other into the skimmer (basket in place). Granules disappeared from both skimmer basket and pump basket in about 6 minutes. Water samples were drawn from the same location in the pool (midway between shallow and deep end) and about 18 inches from the surface. I used a 44 mL sample and 5 drops R-0004 phenol red indicator titrant for the pH test; and a 14 mL sample tube (7 mL sample and 7 mL cyanuric acid reagent) for the CYA test. All sample tubes and collectors were rinsed before testing with sample water and afterward with tap water. The CYA samples were each shaken for 20-30 seconds and titrated into a 9 mL view tube immediately. The temperature of collected sample water was 89° F . At no time was I wearing socks.

Test Results

BEFORE ADDITION
pH 7.7
CYA 30 PPM

AFTER ADDITION
15 minutes
pH 7.5
CYA 40 PPM

30 minutes
pH 7.4
CYA 45 PPM

60 minutes
pH 7.4
CYA 50 PPM

120 minutes
pH 7.4
CYA 50 PPM

24 hours (water temp 87° F)
pH 7.5
CYA 50 PPM

48 hours (water temp 84° F)
pH 7.6
CYA 50 PPM

Epilogue 7/1/2010

In less than one hour 37 ounces of CYA added to the skimmer basket was fully testable (within the limits and precision of the titrated turbidimetric test offered by Taylor). Possible contributors to this rapid absorption: size/speed of pump; clean, oversized cartridge filter (12 PSI); high flow rate and velocity, resulting in quick turnover of pool water (< 3 hours); short run from application point to equipment pad; method of application (warm water and vigorous mixing of slurry, operation of automated pressure-side cleaner, water features, spa overflow); elevated pool water temperature (about 88-89 degrees F.) That’s all I can think of. The implications are: In small pools with warm water, great circulation and a clean filter, the CYA may break down, most of it dissolving in as little as 1/3 of the turnover time.

Questions? Scoffs? Rebukes?