cloudiness and burning eyes

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I tied the sock to a cord and hung it in front of the return jet last night. It was completely dissolved this morning. Is there a reason why it takes 3 days to show up in the cya test?

I also did the quarter test and was able to make out heads or tail. Now I need to figure out how to get the quarters out without going in.


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As far as the CYA question. Even though it's small enough to pass through the sock. It is still not quite small enough to interact with the test reagent. At least that's the way I understand it. I'm sure there are a few folks that have a more technical answer, but mine works for me...

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could you reach the quarters with your sweeper? My pool is small enough that I can reach from one side to the other with it.
 
pabeader said:
As far as the CYA question. Even though it's small enough to pass through the sock. It is still not quite small enough to interact with the test reagent. At least that's the way I understand it. I'm sure there are a few folks that have a more technical answer, but mine works for me...
Click to expand...

Cyanuric acid has a fairly low solubility in water, ~0.2% at room temperature. As a molecule, it is a ring structure (aromatic) and, as pure CYA, is not very polar. The log of the first acid dissociation constant (pKa, or equivalent to the pH at which half the molecules lose their their first hydrogen ion) is ~ 6.88 which makes CYA a weak acid. Now a lot of this changes in the presences of chlorine, but those few simpler facts illustrate why CYA is not particularly good at dissolving in pool water. Also, being a heavier, non-polar molecule, it probably has a low diffusivity relative to other chemicals that we add to our pools.

Here's a simpler way to look at it and an experiment you can do at home - take two tall glasses of still, room temperature tap water. Add a teaspoon of salt to one glass and a teaspoon of sugar to the other glass. You'll notice right away that the salt appears to cloud the water and you can watch it almost dissolve right before your eyes. The sugar, on the other hand, sinks to the bottom and doesn't change a whole lot (in the right lighting, you can see the index of refraction difference between the saturated sugar water at the bottom of the glass and the tap water at the top; you can almost see boundary layer between the two). Let them sit still for about an hour or so. Then, using a straw and your finger, pipette some water off the top of each glass and at varying depths. You'll find that the salt has dissolved and diffused much more extensively in it's glass than the sugar has. CYA is a lot like the sugar in the bottom of the glass - it is slow to dissolve and requires a lot of mixing to make sure it is properly distributed throughout the water volume. But note that, once the compounds are dissolved and mixed, they remain completely mixed and do not segregate or settle out.

This is why it is important to get granular CYA in a part of the pool that has a high flow rate of water - you want lots of fresh water around so that the local concentration is always below 0.2% and you want good mixing to occur. The best place to find those two conditions are in front of a return or in the skimmer basket. In front of the return is a better choice as there is a good, high flow rate of water and the sock of CYA is sitting in a giant water volume, i.e., the pool. The skimmer basket is second best because while it has a very high flow rate of water, the volume inside the skimmer is very low so you could come closer to the saturation point of the CYA if your pool pump is on a low speed or turned off. As well, CYA can lower the pH of water to ~4.5 which, in the larger volume of the pool, makes little difference as opposed to the skimmer where the water volume is much smaller and pH that low could damage plastic or metal parts. Finally, as small undissolved particles of CYA make it through the mesh of the sock, they can get sucked into the filter if the sock is in the skimmer. Inside the filter, the linear flow rate of water is a lot slower than in the pipes and so the CYA can take longer to dissolve or get accidentally backwashed out if hasn't thoroughly dissolved. Small particles of CYA getting through the sock and blown into the pool water volume will eventually dissolve.
 
Let me interject and say Florida gets about 50 Inches of rain annually. As of September you have already received 40+ on average. So your pool doesn't look to have a deep end so the average depth of your pool is likely around 48".

Since you put the CYA in in January, That much rainfall (40") has gone into your pool. There should be little mystery where the CYA has gone.
 
As shown in this map, south Florida has over 60" of water evaporation per year and if the pool water is heated then it evaporates even faster. So that needs to be taken into account, but if the rains are enough to cause overflow of the pool water, then that would dilute the water. If the rains just refilled what evaporated, then there would be no change in the contents of the pool water.
 
duraleigh said:
Let me interject and say Florida gets about 50 Inches of rain annually. As of September you have already received 40+ on average. So your pool doesn't look to have a deep end so the average depth of your pool is likely around 48".

Since you put the CYA in in January, That much rainfall (40") has gone into your pool. There should be little mystery where the CYA has gone.
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OP originally stated they lost 70ppm over a 3 week period.

Dustballs said:
About 3 weeks ago I tested and cya was 70. It's been at 70 for over 3 months.

I was told that the stabilizer paste sticks to the filter and it doesn't burn off. Not sure how I would go from 70 to 0 without draining the water.


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Click to expand...

Dom
 

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Well right now we must assume we have a blank canvas (0 CYA), and an exact known dose. We need to keep an eye on it.

For your FC target, base it on the 70ppm CYA goal now. How long are you currently running the filter?

Dom
 
Dustballs said:
....... Yes I tested CYA about 3 weeks ago prior to my first slam and it was 70ppm........
Click to expand...
I just want to make sure I understand this correctly, when you tested three weeks ago it was 70ppm?

Or the 70ppm was from your first SLAM, and when you tested 3 weeks ago it was 0.0ppm?

Sorry for the Q&A, I want to make sure I fully understand your situation.

Dom
 
Yes. I've been basing it off 70 ppm. I added enough last night to get between 30 and 40 ppm. Will be adding some more after testing on Friday.

Pump has been running for approx 21 hours a day. It turns off at 9pm and when I get home around midnight I turn it back on.


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Here's an update on the pool.

CYA is now at 60. Will add some more to get it up to 70.

Took a dip in the pool and no eye irritation. Also visibility has improved.

Could it be that the low visibility was caused by the chlorine breakdown due to no CYA?


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Clearly the lower eye irritation is due to now moderating chlorine's strength with CYA. It was way too strong with little or no CYA in the water.

As for the visibility, that makes less sense. I think that may have just been some debris in the pool that got cleared out with filtration and was coincidental.
 

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