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?

[waterbear]

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 15 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 [pending]
pH - - -
CYA - - - PPM

24 hours [pending]
pH - - -
CYA - - - PPM

I’ll edit this post to update the last two entries as they become available.

Questions? Scoffs? Rebukes?

I have performed similar experiments and it has taken about 36 hours with pump running for the full amount to show in the best test I had. Then again I was not testing evey hour since it's a waste of reagent, IMHO

Also, by my calculations it should take 37.3 oz of CYA to raise 14k gallon by 20 ppm (and I don't use the pool calculator) so we agree there. Have you verified that your pool is 14k?(There is a way to chemically determine the gallonage of the pool using a modification of the Taylor TA titration to give you a result of 1 ppm and baking soda if you are interested) If not then the experiment should be carried out with testing for a few days until the CYA no longer rises to make sure you have reached the endpoint of your experiment
.
Also the water flow has a lot to do with how quickly it dissolves so this is definitely a case of YMMV. FWIW, when i have used a skimmer sock and put the CYA in that it stayed in the sock for a few hours before there were no traces left. Also, water temp will play a small part here since CYA is very slightly more soluble in hot water(but again, the difference is slight.)
Also, as anyone who has ever broadcast CYA in the pool can attest to, it stays on the bottom for around 6 hours before it seems to disappear. Once again, I believe the water flow, or lack thereof, plays a factor here.
There are really just too many variables which is why it is safe to say retest in a week. This ensures that the CYA has dissolved and that you are not wasting reagent (although those that sell test kits often want you to waste reagents and have to buy refills).


I always told my customers to add it, wait a week and then retest but I always assumed that they were getting at least some protection from UV by the next day.

What I don't get is those that are so afraid of CYA that they add such small quantities for the size of their pool that are barely measurable and wonder why it does not seem to rise. If you overshoot the CYA by 10 ppm it is not the end of the world and probably will have no impact on how you have to care for your pool (Even if you miss the magic number of 50 ppm and end up at 60!) The test is subjective at best so we are really only ballparking it anyway.

[polyvue]

I have performed similar experiments and it has taken about 36 hours with pump running for the full amount to show in the best test I had. Then again I was not testing evey hour since it's a waste of reagent, IMHO

I have too much reagent.

Also, by my calculations it should take 37.3 oz of CYA to raise 14k gallon by 20 ppm (and I don't use the pool calculator) so we agree there. Have you verified that your pool is 14k?(There is a way to chemically determine the gallonage of the pool using a modification of the Taylor TA titration to give you a result of 1 ppm and baking soda if you are interested)

Have gone to great pains to estimate pool volume, including Free Chlorine and Total Alkalinity titrations (I have pages of notes on the latter if anyone is tired of Seinfeld re-runs), geometric summations, various formulae (including one you authored for estimating spa volume, posted on I forget which forum).... of course, all this effort just made me less sure about the correct volume!

If not then the experiment should be carried out with testing for a few days until the CYA no longer rises to make sure you have reached the endpoint of your experiment.

Point taken. We'll see what tomorrow brings.

Also the water flow has a lot to do with how quickly it dissolves so this is definitely a case of YMMV. FWIW, when i have used a skimmer sock and put the CYA in that it stayed in the sock for a few hours before there were no traces left. Also, water temp will play a small part here since CYA is very slightly more soluble in hot water(but again, the difference is slight.)

Yes, I suspect the velocity of the water (elaborated by chem geek in an earlier post), flow rate and temperature have a lot to do with it. I recognize that my pool has a comparatively high rate of circulation and turnover. I don't claim to have overturned any physical law or to have procured magic cya beans that dissolve faster than the usual stock of cya commonly available.

There are really just too many variables which is why it is safe to say retest in a week. This ensures that the CYA has dissolved and that you are not wasting reagent (although those that sell test kits often want you to waste reagents and have to buy refills).

Yes, it's safe (and in some forums, seems to be the law) to suggest waiting "at least a week" before testing CYA. But, like the "filter for a minimum of 8 hours" rule, there are evident exceptions. For good or for ill, my pool seems to be one.

[CarlD]

Our only "laws" are against promoting things that are down-right dangerous because they cause injury, disease or go "Ka-BOOM!!!". We are particularly wary of things that leave you in danger while lulling you into a false sense of security.

Also anything that is not legal or questionably legal is a big no-no here.

[waterbear]

Have gone to great pains to estimate pool volume, including Free Chlorine and Total Alkalinity titrations (I have pages of notes on the latter if anyone is tired of Seinfeld re-runs), geometric summations, various formulae (including one you authored for estimating spa volume, posted on I forget which forum).... of course, all this effort just made me less sure about the correct volume!

If you have not used this method you might want to give it a try. It works.
http://www.poolhelp.com/ChemicallyDe...oolVolumes.pdf

Here is the link for the "“Simplified Formula Numbers” chart
http://www.poolhelp.com/SimplifiedFormulaNumbers.pdf

FWIW, this is the chart I use to calculate dosage amounts for chemicals by using the formmla:
(Volume of pool / "forumula number" for desired chem from chart) x ___ ppm desired change = ___ pound or quarts of desired chem needed

SO for a 14k pool where you want to increase CYA by 20 ppm it is
(14000/120000)x20=
.1167x20=2.33 lbs. CYA
2.33lbs x 16 oz/lb =37.28 (which rounds to 37.3)

[CarlD]

Oh, I forgot: The other BIG law here:

No selling stuff. Period. Ever. No exceptions.

So...what kind of sock is best? Hanes? Gold Toe? Athletic Nikes? Ladies' pantyhose? Colored or white?

I have these great Tilley brand travel socks--soak them in a sink and they dry in 2 hours--"Two pairs will take you around the world!" How do they work?

I mean, how can you compare the "Sock" vs "Skimmer" method unless you can get hard info on how different socks perform?

[AnnaK]

Great links, Evan. Thanks!

[waterbear]

So...what kind of sock is best?

I have always had a preference for seamed nylons on a shapely leg.

[CarlD]

I have always had a preference for seamed nylons on a shapely leg.

TMI, Evan, TMI!

[polyvue]

If you have not used this method you might want to give it a try. It works.
http://www.poolhelp.com/ChemicallyDe...oolVolumes.pdf

Here is the link for the "“Simplified Formula Numbers” chart
http://www.poolhelp.com/SimplifiedFormulaNumbers.pdf
[...]

Yes. This is the source for the formula I used in the spring when estimating volume via Total Alkalinity. Even this technique has its drawbacks but it requires absolutely no vector calculus, an advantage for those of us whose mathematical aptitude and/or enthusiasm declined sometime before or during Calc I.

I mean, how can you compare the "Sock" vs "Skimmer" method unless you can get hard info on how different socks perform?

You're correct; no attempt at a comparison was made. Nor could I figure out how to introduce a meaningful control (having run out of duplicate in-ground free-form swimming pools that were designed and built to my specification); and, besides another test in the same pool, how does one evaluate the repeatability of this experiment?

As Evan pointed out earlier (and AnnaK, above), too many variables. Perhaps my hand was shaking when I titrated (perhaps my hand always shakes but I'm unaware).