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Thread: CYA in a sock

  1. #21
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    Default Re: CYA in a sock

    All this may be true for your pool. My experience has been that it takes longer for my pool to get up to the reading that I aim for when I add cya. So, although in some pools it may be in there and measureable fairly quickly, for some pools that doesn't always appear to be the case. Therefore, when I answer posts, I will still continue to advise people to wait awhile before testing again (to save reagents) or adding more. Better to be a little patient that overshoot a target of cya since it could mean a partial drain and refill.

    Thanks for sharing!

  2. #22
    chem geek is offline PF Supporter Whibble Konker chem geek 4 stars chem geek 4 stars chem geek 4 stars chem geek 4 stars
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    Default Re: CYA in a sock

    Personally, I've used an old T-shirt put into the skimmer and then added CYA on top of that shirt in the skimmer. It is important to note that my skimmer has a pipe going into the pool (looks like a return below the skimmer inlet) so that any skimmer clog will pull in water from the pool (and not crack the skimmer). I also have two floor drains so even if the skimmer and it's separate pipe to the pool were clogged, the pump would still be able to pull water from the floor drains.

    So for me this works best as it is easy to do. The CYA dissolves in a matter of hours, usually overnight and certainly less than 24 hours. As for CYA measurement thereafter, at least 2/3rds of it registers after it dissolves (tested 24 hours after my last addition to the skimmer) and it could be more, but I don't usually add more than 20-30 ppm and target a CYA of 30-50 ppm so errors in measurement play a significant role here.

    When CYA is added to the skimmer without a T-shirt, panty-hose, skimmer sock, etc. then it gets caught in the filter. The water velocity in the filter media itself is MUCH slower since it is spread over a much larger area. This is why it takes longer for the CYA to dissolve using this method. For my oversized cartridge filter with four 85 square foot filter cartridges, even with the pump at 48 GPM for my solar (it's 26 GPM with no solar), over 340 total square feet of cartridge area the water velocity is around 0.2 inches per second. In my skimmer (with no CYA in it that obviously blocks the flow significantly), assuming 15 GPM and a 1 foot diameter skimmer area the flow rate is about 2" per second.

    Those that use a sock over the return should probably periodically squeeze the sock to break-up and mix-up the material inside. I think that a sock over the return is far better than simply broadcasting the CYA around the pool, but I think that putting the CYA into the skimmer either with a T-shirt/panty-hose/skimmer sock filter or without (to get caught in the filter) are very reasonable alternatives. Just make sure the filter isn't backwashed too soon -- the recommendation to wait a week should be fine (or if a CYA test shows that it is all dissolved).

    Richard
    Last edited by chem geek; 06-30-2010 at 02:54 AM. Reason: corrected "later area" to "larger area"

  3. #23
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    Default Re: CYA in a sock

    Hadn't thought about the water velocity thing -- makes sense.

    Ben

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    Default Re: CYA in a sock

    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?
    Last edited by polyvue; 07-01-2010 at 07:07 PM. Reason: Added final test results & epilogue
    16'x29' free-form 14K gal IG gunite pool; SWCG & sodium hypochlorite 8.25%; Hayward SwimClear C4025 cartridge filter; Hayward SP3202VSP TriStar Variable Speed Pool Pump; custom test kit based on Taylor K-2006C; city; PF:8.6

  5. #25
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    Default Re: CYA in a sock

    Quote Originally Posted by polyvue View Post
    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.
    Retired pool store and commercial pool maintenance guy.

  6. #26
    chem geek is offline PF Supporter Whibble Konker chem geek 4 stars chem geek 4 stars chem geek 4 stars chem geek 4 stars
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    Default Re: CYA in a sock

    Quote Originally Posted by polyvue View Post
    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.
    I want to be clear I understand this. So the slurry of CYA didn't have the CYA dissolve much and when you poured this into the skimmer you didn't have any skimmer sock, panty hose or T-shirt, right? So the CYA didn't all go through the small skimmer holes right away and that took around 6 minutes -- was that for each addition or 6 minutes for both gallons combined?

    I wonder how long it would take for some CYA to dissolve in a tube with a magnetic stirrer (I know some of you out there have one)?

  7. #27
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    Default Re: CYA in a sock

    Quote Originally Posted by chem geek View Post
    I want to be clear I understand this. So the slurry of CYA didn't have the CYA dissolve much and when you poured this into the skimmer you didn't have any skimmer sock, panty hose or T-shirt, right? So the CYA didn't all go through the small skimmer holes right away and that took around 6 minutes -- was that for each addition or 6 minutes for both gallons combined?
    Actually, there was quite a bit dissolved in the time it took to add warm water, stir it up and deliver it to the skimmer. The slurry was pretty cloudy so I would guess that about a quarter of the granules had partly or completely dissolved before being poured in. No skimmer sock or any other material in place -- just the skimmer basket. 2 consecutive applications of about 1 gallon each were poured in 30 seconds apart (I followed each with a bucket of pool water to ensure that the granules adhering to the sides were flushed into the basket). It was at that point that I thought to set my timer and kept an eye on the skimmer while the granules escaped/dissolved. I didn't see any granules left at about 5 minutes and only a few in the pump basket -- they too disappeared, about a minute later. So, I'd say 6-7 minutes elapsed from the moment I finished adding the second bucket. During the 6 minutes I entertained myself by varying suction from 0 to 100%, but most of the time it was at mid-point (50% main drain, 50% skimmer).

    I should note that the last time I checked there were a few granules (20?) lodged in the transparent Jandy Energy Saver Filter that was mis-plumbed in the water feature (deck jet) return line. This is pretty typical. If I don't run the jets they'll sit there for weeks or months, undisturbed.
    Last edited by polyvue; 06-30-2010 at 03:37 AM. Reason: addendum
    16'x29' free-form 14K gal IG gunite pool; SWCG & sodium hypochlorite 8.25%; Hayward SwimClear C4025 cartridge filter; Hayward SP3202VSP TriStar Variable Speed Pool Pump; custom test kit based on Taylor K-2006C; city; PF:8.6

  8. #28
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    Default Re: CYA in a sock

    Quote Originally Posted by waterbear View Post
    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.
    16'x29' free-form 14K gal IG gunite pool; SWCG & sodium hypochlorite 8.25%; Hayward SwimClear C4025 cartridge filter; Hayward SP3202VSP TriStar Variable Speed Pool Pump; custom test kit based on Taylor K-2006C; city; PF:8.6

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    Default Re: CYA in a sock

    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.
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    Default Re: CYA in a sock

    Quote Originally Posted by polyvue View Post
    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)
    Retired pool store and commercial pool maintenance guy.

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