Cloudy pool water

Causes and cures for cloudy swimming pool water.
Milky pool water, white, pink, brown, purple, black cloudy water.
clsmits
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Cloudy pool water

Postby clsmits » Mon 06 Jul, 2009 16:59

My pool is three years old, partially inground, and has been great until now. This morning I uncovered the pool to find cloudy water. (This is the first time I have not kept up with my testing and treatments. It was cold last week and then we went on vacation so it has lacked attention for almost two weeks.) My levels are all normal other than free chlorine. I've super chlorinated three times today and my free chlorine is still zero! How much can I add before I create another problem? My total chlorine is at 3. I'm really afraid of messing up the Cyanuric acid levels.


chem geek
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Cloudy pool water

Postby chem geek » Mon 06 Jul, 2009 18:11

Get chlorinating liquid or bleach and hit the pool hard with it -- adding 10 ppm FC at a time until you get a measurable FC reading with a good test kit (one that does not bleach out). Algae will take a lot of chlorine initially, but will then require less as the pool starts to clear. If you can't get chlorinating liquid or bleach and your Calcium Hardness (CH) level is low, you could use Cal-Hypo pre-dissolved in a bucket. With any concentrated chemical, pour it slowly over a return flow at the deep end with the pump running. For extra safety in vinyl pools, lightly brush the side and bottom in the area where you've added chemicals to ensure thorough mixing.
clsmits
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Joined: Mon 06 Jul, 2009 16:47

Cloudy pool water

Postby clsmits » Mon 06 Jul, 2009 20:10

Thanks. I will give that a try, and I'm guessing it'll take care of it. Is liquid chlorine stronger than pool shock?
chem geek
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Cloudy pool water

Postby chem geek » Mon 06 Jul, 2009 20:59

The strength is irrelevant since in the water chlorine is chlorine. Chlorinating liquid is less concentrated than solid/powder forms of chlorine, but it's also less expensive per pound. Per actual chlorine amount, it's actually less expensive if you account for the other pH adjustment chemicals needed with other products.

Just get the Free Chlorine (FC) level up to 40% of the Cyanuric Acid (CYA) level unless the CYA is very high (80+) in which case you should dilute the water by a partial drain/refill to lower the CYA level. Read the Pool School including the article on Defeating Algae for more info.
clsmits
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Pool Newbie
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Joined: Mon 06 Jul, 2009 16:47

Cloudy pool water

Postby clsmits » Tue 07 Jul, 2009 19:57

My pool is looking quite clear now. Not perfect, but MUCH, MUCH better. However, the chlorine that worked to clear it up is quickly used up! Also, my ph and cya levels keep dropping. Will more shock correct this problem? Or do I need to do something else?
chem geek
Pool Industry Leader
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Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Cloudy pool water

Postby chem geek » Wed 08 Jul, 2009 00:51

The pH will drop as the FC level drops since the consumption/usage of chlorine is an acidic process. I don't know why your CYA is dropping -- it shouldn't. Perhaps the water was so cloudy as to interfere with the CYA test earlier making you think it was higher than it actually was.

The chlorine will get used up quickly if there is still stuff to oxidize in the pool -- usually the chlorine drops the fastest when initially attacking an algae bloom and gets used up less later. See what the FC drop is overnight (assuming you have a FAS-DPD chlorine test so you can measure high chlorine levels accurately). If it's > 1 ppm drop, then this is chlorine clearing the pool. If the drop is <= 1 ppm overnight but the loss is larger during the day, then you may not have enough CYA in the water for the amount of direct sunlight on your pool.

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