Calcium Hypochlorite

I've been reading up on pool water chemistry, sanitizers, chlorine, ORP and CYA.
This of course _after_ opening up my pool (new pool owner) for the first time. And of course after a visit to my friendly neighbourhood pool store, who sold me all these chemicals to balance the water. What gets me is that you never buy Cyanuric Acid you buy a product called "Protect 20", you never buy baking soda you buy "PH+", you never buy borate (still haven't figured that one out) you buy "Optimizer Plus" and so on. This bugs me, I want to know what I'm buying, and this is what got me reading.
So it seems that the "Protect 20" bottle I bought was indeed CYA, and the whole bottle went right in (I forgot the bottle size) to my 18ft above ground pool, per the Pool Store's instructions.
In my readings I've come to the conclusion that by regular use of stabilized chlorine, one sees the sanitizing effect of chlorine go down and down as the level of CYA increases (and there's some already in there). Note that we're somewhat 'lucky' here in my region in that we get to flush out 2/3 of the pool water when we close 'em down for the winter, so out it goes in autumn.
Now this was before I got educated. I plan to get the CYA level tested sometime today.
For chlorination, I'm manually feeding granular chlorine to the pool after dissolving it in a bucket of hot water. This I do when the OTO reading falls below 1.5 ppm. (Yes, the DPD test kit I bought online is on its way to me soon.) This routine works well for me, however I'm open to suggestions on better ways.
This granulated chlorine I bought late last year does not mention anything about being stabilized, and no mention of "dichlor". It just says "Calcium Hypochlorite, oxygenated". What exactly is in there? There are no other indications.
Also, the "Cyanurics, Benefactor or Bomb" article mentions 20 ppm as a level for manually treated pools. This seems a bit high, what are people's thoughts on this. I'd say 5-10 ppm.
Had I known about CYA before opening my pool, that "Protect 20 " thing would never had gone in there.
I've also noticed some really conflicting information on chemistry, the document from the Missouri of Health mentions no adverse affect of CYA on CA. Interesting...
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Paul Giroux writes:

The pool store biz is based on sheepish customers. They do not like for people to know what is going on (and most people don't care or don't have the education anyway). Just buy what they say. It is annoying that if you *want* to know, they won't tell you except as the law requires.

I doubt that it has been cyanurated. Cal hypo is chlorinated lime. The economics of production do not favor purity and thus you only get a 65 percent product, the rest shows up as insoluble sludge you have to decant.
Does it give a figure for "available chlorine"? This is the mass (as a proportion) of chlorine gas that would give the equivalent chlorine concentration as the product, and give you some hints as to constituents. Cal hypo only yields 50s or 60s as percent. Cyanurated stuff can exceed 100 percent (only half of gas chlorine actually being "available").
Dunno what "oxygenated" means. Googling "calcium hypochlorite oxygenated" yields 0 hits. Some blending of a non-chlorine oxidizer component?

URL?
"Government" reports (extension agents and the like) can be utterly stupid or repeating factoids.
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Glad you responded to my post Richard. I have read a lot of what you have posted, including your garage door spring replacement page and the stop order you received for the plumbing work you did. Highly interesting.
If I remember, as I am writing this from the office, it did say something like 65% available chlorine. I'll confirm when I get back home tonite. It was a bucket I bought from the local hardware store.

That sould have read CYA on chlorine. Sorry.
http://www.dhss.state.mo.us/ehcdp/PoolSpaChem.pdf
Some notable quotes:
P 14 "Cyanuric acid bonds with the available chlorine in a manner that does not use up the chlorine. At high stabilizer levels (over 100 ppm), chlorine's efficiency may be reduced"
P 21 "'Chlorine Lock,' a term given to a condition once thought to be produced from high cyanuric-acid levels tying up free available chlorine, has been proven false by the industry. Generally, high cyanuric acid levels of 400 ppm or higher are associated with excessive Total Dissolve Solids (TDS) or combined chlorine or chloramines and not "Chlorine Lock".
P 50 "Both the granular and tablets have a by-product known as cyanuric acid which is the only known chemical that stabilizes a free chlorine residual without interfering with its sanitizing effectiveness."
A few more questions: (1) Would too much CYA show up as a "low" pH reading? (2) What is the effect of adding zinc to pool water? The newest fad are these chlorine pucks that contain zinc, I forget the name, z-pucks I think, supposedly much better than its direct competitor, http://www.crystalplus.ca/UntitledFrameset-9.htm . Note the information-free web page...
Thanks again.
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Paul Giroux writes:

This reads like a high school term paper. Some good information, but mostly sounds like it was copied from mfr sales brochures and news releases.

No. While it is an acid, it is only a small contributor to the pH.

Zinc, like copper or silver, is poisonous to some bacteria and algae. Metal algaecides are cheap, effective, and likely to stain your plaster.
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This is what is actually says:
"Guarantee Calcium Hypochlorite 65% Available Chlorine Content 65%"
(1) I know I have it somewhere but what exacly is the difference between these two numbers?
Also I do beleive it's not stabilized as it says on the pail "NOTE For outdoor pools, chlorine residuals can be protected from destruction by the sun's rays by addition of stabilizer (cyanuric acid).
Thanks again for your help, Richard.
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Paul Giroux writes:

This reflects the economics of production. 65 percent purity is the cheapest way to deliver the desired cal hypo, with the balance being inert byproducts of chlorinating lime.

Means that 1 lb of this powder will be as effective as 0.65 lb of pure chlorine gas when used as a sanitizer, the gas method being the benchmark for sanitation with chlorine. Chlorine gas is used in water treatment plants and big commercial pools, is cheaper than any other chlorine compound, but isn't legal for homeowners due to hazmat handling issues (a tank leak is easily deadly).
The "available chlorine" figure is an industrial chemistry term which does *not* mean that 65 percent of the molecular weight of the compound is contributed by chlorine atoms. Should actually be about half the molecular weight of chlorine (proportioned to the purity) since only half of each Cl2 molecule in gaseous chlorine produces hypochlorous acid. In other words, a compound partly of chlorine can dissolve all of its chlorine atoms as hypochlorous acid, and so theoretically could exceed 100 percent "available chlorine". This is why you see figures like "99 percent available chlorine" on dichlor and trichlor products. I suspect the mfs deliberately weaken dichlor/trichlor to 99 percent to sound "strong" and to avoid confusing people with an above 100 percent figure.
That both numbers on your bucket happen to be 65 percent is just coincidental.
Liquid sodium hypochlorite solution is only something like 10 percent "available chlorine", since it is diluted with so much water for stability and safety. But despite the perishability and chore/risk of hauling all that liquid, it is still the cheapest consumer form by weight of chlorine where I live in Florida.
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I understand from your web page that you keep your ORP at 650mV. Is this right? Also what ORP meter are you using. I'm currently looking at an Oakton portable, seems like a good product. Finally, what are your thoughts, and what accuracy should one aime for, if using digital pH meters?
Thanks.
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Paul Giroux writes:

I use a Corning ORP-65 hand-held item, but I don't think they make it any more. Meters for pH are hard to maintain accurately, what with wet bulbs and all. You need about 0.1 pH accuracy or better to monitor a swimming pool.
You also need access to standard solutions to check calibration.
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I finally got my hands on a 0.01 accuracy pH meter and an ORP meter, and will obtain pH calibrating solutions from my local lab supply store. I understand the principle in calibrating the pH meter in one, two or three points using 4.00, 7.00 and 10.00 pH solution (I'll do 7 and 10), but how does one calibrate/verify an ORP meter ? Can I make some sort of solution that will have a specific mV value? I can feed 500mV with my bench PSU but that will only test the electronics, I want to make sure the probe is okay.
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If its more convenient Grainger carries buffer solutions, or the materials needed to make them. That's all I use to calibrate my pH meters.
RB
Paul Giroux wrote:

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Paul Giroux writes:

Try http://www.omega.com to see if they have calibrating solutions.
I would consider making your own rough version diluting a few drops of fresh sodium hypochlorite (and some hydrochloric acid to lower the pH to your pool's typical level) in distilled water vs the distilled water alone.
This is just a check; the ORP meters I've seen don't need calibration like pH. But ORP elements somehow wear out and quit responding after a while.
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I understand then that they're just like voltmeters, and my voltmeter didn't need calibration when I bought it, and that the only thing to check basically is that the electrode is not clogged up.
If the electrode responds well to a wide span of ORP values (water vs water+Cl) then it isn't "degraded", and if the meter shows 650mV for my pool water then that's the actual value give or take the accuracy of the unit (5mV), assuming everything else (pH, temperature ...) stays constant, right?
Theoretically then I would be able to buy an electrode, perhaps a 'preamplifier' and hook it up to my DVM and read the value off the mV scale.
Sorry to be picky but I'm somewhat confused. What I'm trying to do in the long term, is to track the ORP value of my pool water and use *that* instead of the FAC/CC values to determine water "health". It seems more complicated that I originally thought.
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Paul Giroux writes:

Well, "just" a voltmeter, except that it is immersed in an oxidizing fluid. (You're measuring that oxidation potential, remember.) Thus you have electrodes with thin layers of durable but expensive things like platinum, which still erode. Sensing ORP is inherently non-durable.
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