Chlorine tablets and granulated chlorine

Chlorinating, maintaining the right chlorine levels,
chlorine problems. Dichlor, trichlor, cal hypo, bleach,
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Chlorine tablets and granulated chlorine

Postby sparkwaterceaner » Sat 20 Oct, 2007 18:24

I've got a 40,000 liter pool (dunno how much in gallons).
The label on the container of the granulated chlorine I use says to dose 80 grams per day on summer (here in the south hemisphere it is spring), and , on the other hand, the label on the container of chlorine tablets says to dose 2 tablets per week in summer.
The problem is that when I stick to what both say, chlorine levels skyrocket (although I put them on the pool at night and measure with the test kit at midday next day).
What should I do, keep on with the tablets and put granulated chlorine once a week? Neither label tells anything about combining both tablets and granulated chlorine!


Postby sparkwatercleaner » Sat 20 Oct, 2007 18:27

Note: Both tablets and granulated chlorine add stabilizer
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Postby mr_clean » Sun 21 Oct, 2007 12:47

what ever you perfer for your pool is what to use. You already know they both add CYA so you can keep an eye on level. If it bothers you they do both add CYA then use liquide chlorine and when CYA is needed use leftover chemicals you have to raise level.

40,000 liters is around 10,500 gals
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Postby sparkwatercleaner » Mon 22 Oct, 2007 15:53

What is CYA???
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Postby chem geek » Mon 22 Oct, 2007 17:29

CYA is Cyanuric Acid aka stabilizer aka conditioner. It protects chlorine from getting broken down from sunlight, but it also combines with chlorine to form relatively inert compounds thereby reducing chlorine's effectiveness as a disinfectant and oxidizer. So a little CYA is good, but too much is not. You can keep the chlorine disinfection level fairly consistent by keeping the FC to CYA ratio roughly constant. To keep away algae without using an additional algaecide, you should have an absolute minimum FC level of 7.5% of the CYA level -- so 30 ppm CYA needs a minimum of 2.2 ppm FC while 80 ppm CYA needs a minimum of 6 ppm FC. For extra safety, especially when manually dosing with chlorine, using a target FC of 11.5% of the CYA level is better.

If you want the disinfecting chlorine level to be lower or if you don't think you can consistently maintain the FC level, then you should use an algaecide such as PolyQuat 60 on a weekly basis. You can then have the FC level be lower -- perhaps at 3% of the CYA level -- which is still enough to kill most bacteria though not enough by itself to inhibit algae (but is enough along with the algaecide to do so).


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