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Thread: CYA in a sock, myth or big help?

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    JasonLion's Avatar
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    CYA in a sock, myth or big help?

    The idea of putting CYA in a sock, instead of directly into the skimmer, has been around for a while. In theory using a sock solves a problem. Keeping the CYA out of the filter allows you to backwash the filter freely. Otherwise you have to remember not to backwash the filter, which can be a pain to remember and is occasionally required due to rising filter pressure. This is most commonly a problem when fighting algae while opening the pool, when frequent backwashing is often needed and having to add CYA is also fairly common.

    I used to think that the sock approach was a great idea. But some recent feedback has got me wondering if it really works the way I used to think that it worked. Several people have reported that CYA disappears from their sock in under a day, occasionally in just a few hours. CYA doesn't dissolve in just a few hours for me. The CYA level has kept rising for at least three days, quite possibly more, after I pour CYA in the skimmer. (I don't normally use a sock because it is more work that way and I can count on myself not backwashing.)

    I am beginning to wonder if perhaps the CYA is breaking into particles fine enough to get through the sock, but not completely dissolving. Another possibility is that there is some new CYA manufacturing technique that allows it to actually dissolve more quickly if you have the right "kind" of CYA. Or is there some aspect of the water chemistry or temperature that affects the rate of dissolving that I am unaware of?

    I looked at the CYA packages I have around. One, from Lowes, says don't backwash for 24 hours, the other, from Leslie's, says not to backwash for at least 72 hours. Is that because the products are different? Or just random variations in directions for the same product?
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    Prior years I would add the cya to the skimmer, which had a skimmer sock on the basket(socks on all season). Two pounds would be gone overnight. But my cya levels never matched my expected goal. Since fighting the opening algea problem of backwashing, I must have been loosing the cya before it was completely dissolved in the filter.

    This year I added the cya to a skimmer sock tied to my steps. The sock was across from the return in the steps which caused a nice constant flow to the cya. Not a strong return right in front of it. Kind of like a tea bag steeping in a BIG cup of water.

    It took about 5 days for the cya to dissovle. With me squeezing the sock, you can see very fine particles leaving in a white cloud. The cya reading was correct after everything was gone.

    I still had to backwash for the spring cleanup. My skimmer sock method allows me to see when the cya very close to being completely dissolved.

    Joe
    Joe

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    Guest
    The ONLY reasons to put CYA in a sock is because you don't have a skimmer or if you are trying to raise the levels while you are fighting algae. In the second case you will lose some CYA when you clean the filter but not the whole amount since part of the undissolved CYA stays in the sock. Otherwise just pour it in the skimmer, have some patience, and test it a week later.
    If yo search on the different forums you will find time afte time where someone added CYA and it seemed to disappear but it was not showing up on testing after a day or two. However, when they retested a week later it showed up. The luckly ones did not add more CYA but there have been some instances that I remember where the just did not have any patience and ended up having to drain some of the water out to lower the level. If the water temps are very cold CYA can be even slower to dissolve.
    As far as how long to wait I have seem manufacturers instructions that gave a waiting time from 20 hours to 1 week yet the CYA looked to be the identical granule size. I have also seen instructions that said to predissolve it in a bucket of water, However, they don't tell you how long that will take! Perhaps you need to let the bucket sit for a few days because if you try and pour your CYA in a bucket you will find that most of it does NOT dissolve.
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    Quote Originally Posted by joenj
    With me squeezing the sock, you can see very fine particles leaving in a white cloud. The cya reading was correct after everything was gone.


    Joe
    And if you see very fine particles then the CYA is NOT dissolving in the water but dispersing. It might take an additonal day or three for it to completely dissolve.
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    mas985's Avatar
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    Quote Originally Posted by waterbear
    Quote Originally Posted by joenj
    With me squeezing the sock, you can see very fine particles leaving in a white cloud. The cya reading was correct after everything was gone.


    Joe
    And if you see very fine particles then the CYA is NOT dissolving in the water but dispersing. It might take an additonal day or three for it to completely dissolve.
    This has been my experience as well. When the CYA passes through the skimmer sock, I see very small particles which means it has not total dissolved. However, I do think that since the particles are smaller than what they started out as, the CYA may end up dissolving slightly faster via the sock method. When I put CYA in via the skimmer, it took over a week to stabilize while with the sock method it disappears in a few hours but shows up in the measurement within a few days so overall it seems to have speed things up a bit.
    Mark
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    I have never placed CYA anywhere but my skimmer. Obviously, I can't backwash during that 3-5 day period it seems to take for the CYA to register the correct ppm on the test.

    I do believe it dissolves and subsequently registers somewhat quicker using the sock method. Nothing scientific to support that but the anecdotal evidence on TFP and PF seem to support that.

    That said, I would not recommend the sock method in any case except clearing a green pool for all the aforementioned reasons. My unscientific guess is that you would lose very little (less than 5ppm) CYA even if you backwashed daily during the dissolving period. You simply would not backwash (and lose) more than 5% of your water But, the sock method seems like an additional hassle to me and I am really big on keeping a clearing process as simple as possible.
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    Okay, this may be a dumb question, but what the heck...

    My skimmer connects to the filter pump through those black flexible hoses with the ridges and it lays on the ground for a little ways. If I dump CYA right into the skimmer, could some of it get trapped in those ridges and take longer to dissolve?

    Also, isn't it bad for the pump for gritty stuff to get into it? I kind of thought that was the reason for the sock method until recently. Or are the CYA particles small enough that it doesn't affect the pump?
    Sue

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    I think both of those possibilities exist but they have minor affect. Some CYA could settle a little in the pipe but that water moves thru there pretty fast and it would be pretty quickly dissolved from the rapid flow of water over it.

    Yeah, it's probably a little gritty but it's actually not very rock-like, probably softer than the plastic on the pump impellor, so it breaks rather than scratch the impellor. Of course, the impellor is only exposed to it for a short time before it's in the filter. However, I would never recommend to anyone that that be an everyday occurence. It obviously causes some stress on the pump parts and not something you would subject it to over and over.
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    JasonLion's Avatar
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    So it seems like the granules of CYA are breaking up into small bits that are not yet completely dissolved. That means that putting a sock in the skimmer will lead, in a few hours, to the exact same result as pouring the CYA directly into the skimmer. The CYA will break up at some medium fast rate and end up in the filter either way.

    Putting a sock with CYA somewhere else, far from a skimmer, presumably leads after a few hours to fine CYA dust, some in the sock and some all over the pool. That would mean much less CYA in the filter. Some of the dust would end up in the filter, and some of it would presumably settle down on the bottom.
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    Mod Squad JohnT's Avatar
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    I think the sock is somewhat of safety net in case you have to backwash, but I doubt it accelerates the process any. Another issue is that some pools seem to dissolve CYA very quickly and some take days. I can throw a sock in the skimmer in the evening with enough CYA to raise my water 10ppm, and it is gone the next day when I get home from work. By the next evening my CYA will be 10ppm higher. Evan, I believe you've posted before that your pool dissolves CYA quickly??

    Maybe the 7 days to test after adding CYA is a subject for discussion as well.
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    That means that putting a sock in the skimmer will lead, in a few hours, to the exact same result as pouring the CYA directly into the skimmer.
    Epiphany!! (On my part, anyway) I don't think the sock method was EVER intended to be put in or near the skimmer but, rather, suspended in front of a return. The idea being for the return flow to dissolve CYA out of the sock (perhaps into finer particles but, ideally, to actually go to solution)

    That may explain some of the confusion over the CYA loss of the sock method. Certainly, suspended in or near a skimmer, I would see no reason for the sock. But, suspended in front of a return is what I have always seen pictured and, in that scenario, it makes a lot of sense.
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    The 7 days is a 'safety net" just to make sure everything dissolves. In reality it's all probably gone in about 4 days but if the water is very cold it can take longer. I HAVE found that running the pump 24/7 does speed it up, based on the amount of CYA in the water by testing and NOT by the amount that has appeared to dissolve. I actually put my CYA in the skimmer in a skimmer sock that is always on my skimmer basket and all the CYA is usually gone from the sock in about 12 hours BUT it does not show up on water testing for about 3 or 4 days. The only reason I pour it in like that is that I am too lazy to remove the skimmer sock or basket before I put it in. Why make extra work?

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