Very High Chlorine After Shocking

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Very High Chlorine After Shocking

Postby Eric » Fri 01 Jun, 2007 10:38

For the first time the year, I shocked my pool (in ground, vinyl, about 12,000 gal.) with 1 lb Power Powder Plus. Before the shock, the chemistry measured fine -- 3 ppm chlorine, 7.2 pH, 140 ppm total alkalinity. 48 hours after adding the shock, the chlorine level is off the scale of my test kit. The color is orange, not yellow. I estimate it's at least 20 ppm chlorine.

Why did the chlorine go up so high? This amount of Power Powder Plus should have raised the chlorine to around 13 ppm. And why is it taking so long to come down? Should I just wait for it to come down or add chlorine reducer?

Thanks.
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Postby Buggsw » Fri 01 Jun, 2007 10:58

You may have a high CYA/stabalizer and the cal hypo you put in add more stabilizer.
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Postby Buggsw » Fri 01 Jun, 2007 11:01

Argh, this forum is so quirky, it wouldn't let me edit my response to change the word add to added.

I was afraid you would think I said to add more CYA. Don't do that.

You probably already have high CYA and CAl Hypo (the Power powder) also adds CYA.
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Postby Eric » Fri 01 Jun, 2007 11:30

Buggsw, thanks for the reply and information.

I did take the solar cover off the pool. This should allow more UV light to reach the water and degrade some of the chlorine today. It looks like the only way to lower CYA is partially drain and refill. I would rather wait another day or two and see is chlorine goes down. Though if CYA is too high, this will be an ongoing problem.
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Postby Buggsw » Fri 01 Jun, 2007 16:27

Sounds like a good plan. Yes, leave the cover off.

Get your water tested. Don't worry about dumping water unless your CYA is too high. CYA is good but too much is bad in that it takes more and more chlorine to combat CC's.
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Update

Postby Eric » Thu 07 Jun, 2007 10:37

It took a few days, but the chlorine level is now normal, 2 ppm.

Also, according to the Leslie people, Power Powder Plus is calcium hypochlorite and does not contain a stabilizer (CYA). Adding Power Powder will not increase CYA levels. The trichlor tablets I'm using do contain stabilizer.

Finally, I'm using a floating chlorinator in the pool. I only need to add one 3" trichlor tablet a week to keep the chlorine level reasonable. Any more than this, and the chlorine level gets too high. In reading this board, I see others need at least one tablet a day. Does this seem reasonable?
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Postby Buggsw » Sat 09 Jun, 2007 16:30

Good to hear you are now at good levels.

The pucks will add CYA to your pool. As long as your CYA is within the low end of the 30-50 range, it's okay to use them.

About other people and the amount they use - well, it's all relative to their location and chemistry of their pool. Each pool is different and you will learn the recipe that works for your pool.
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Postby mrdwpman » Mon 30 Jul, 2007 14:02

great information. I just got a new 6800 gal easy set pool and i also shocked it and my clorine is off the scale. I will check it again in two days.
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Re: Update

Postby Backglass » Mon 30 Jul, 2007 14:29

Eric wrote:Also, according to the Leslie people, Power Powder Plus is calcium hypochlorite and does not contain a stabilizer (CYA). Adding Power Powder will not increase CYA levels.


Calcium Hypochlorite will however raise your PH and Total Alkalinity.
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Postby chem geek » Wed 01 Aug, 2007 16:38

Cal-Hypo is calcium hypochlorite and is very similar to sodium hypochlorite which is bleach or chlorinating liquid except that Cal-Hypo contains calcium so will increase Calcium Hardness (CH). For every 1 ppm Free Chlorine (FC) added by Cal-Hypo, you also increase CH by 0.7 ppm.

Both Cal-Hypo and bleach / chlorinating liquid will increase pH (and TA a little) temporarily, but as the chlorine gets used up, this is an acidic process and the pH (and TA a little) will come back down. There may be more extra base in some Cal-Hypo brands, but mostly it doesn't look like a lot. So really, the main thing to watch when using Cal-Hypo is that in increases CH. Also, note that it doesn't dissolve quickly so should be pre-dissolved before adding it to the pool, especially a vinyl pool, or else it will settle on the bottom and produce high chlorine levels locally until it fully dissolves (above-ground pools also tend to have poor circulation at depths because they usually don't have a floor drain).
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