Cloudy pool water for 2 months

Causes and cures for cloudy swimming pool water.
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Cloudy pool water for 2 months

Postby Pool mail » Sun 27 Jan, 2008 03:09

What is the problem when you have dumped all of the following into a pool:
(not all at the same time) black/ green algea killer, 5 gallons of shock a week for the past few weeks, stablizer, acid.

My pool has been cloudy for 2 months now and I have dumped several hundred dollars into trying to get it back into shape. The ultimate problem is that despite all of the shock and such the chlorine level continues to read at nothing.

Please advise if you have any suggestions to offer.I am at my wits end! Thanks in advance for your time on the subject.

chem geek
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Postby chem geek » Sun 27 Jan, 2008 03:51

High levels of stabilizer (Cyanuric Acid, CYA) reduce chlorine's effectiveness and that also includes slowing down the rate at which it kills algae. It usually takes a sustained Free Chlorine (FC) level of 40% of the CYA level to kill algae relatively quickly (an FC of at least 20% of the CYA level to kill it slowly, and 7.5% of the CYA level to prevent algae in the first place). You should only use unstabilized chlorine for shocking, usually chlorinating liquid.

If you have a Taylor K-2006 test kit here (or a TF100 test kit from tftestkits(dot)com here) then measure the CYA level. If it's very high (say, above 60 ppm), then it's usually easier to do a partial drain and refill to lower it before killing the algae with lots of chlorine -- not just once a week of shock but a sustained effort several times a day for the first days and then at least once a day after that -- the key is keeping a high FC level as much chlorine will get consumed killing the algae. Don't get discouraged -- see this post for a pool with algae upon spring opening that was cleared using chlorine alone (but the CYA level was not too high).

Your other alternatives are to use a copper-based algaecide or a phosphate remover, but the copper has a side effect of possible staining while the phosphate remover can be expensive. Test the water for phosphates and if they are above 3000 ppb then use a phosphate remover. Otherwise, you just haven't killed the algae growth with a high enough FC level relative to CYA level and I suspect the CYA level may be very high. If you've been using Trichlor tabs as your normal source of chlorine, then that is likely to be the problem since for every 10 ppm FC added by Trichlor, it also adds 6 ppm to CYA and the CYA accumulates over time and does not go away the way that FC does.


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