severe green pool color

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mike v

severe green pool color

Postby mike v » Thu 20 Sep, 2007 08:01

my pool water is green,i don't want to call it algae because nothing i am doing is getting rid of it..i have tested my pool water and had it tested and the following data is ph 7.5,alkan 180,hardness 200,cya 60 cholrine 4.0

yesterday sept 19th i followed the same suggestion i am getting i shocked it again with 3 bags of turboshock and followed that with 20 ounces of algae killer.
my pool is 24 ft round above ground the filter has been running 24/7 for the last 2 week this green color showed up 3 weeks ago. i have scrubbed the entire pool 3 twice and have backwashed a minimum of 10 times this pool was put in this june . and was fine all summer i tried maintaining the proper data every week.

anybody have any good sound fix
i am located in western pennsylvania. :cry:


chem geek
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Postby chem geek » Thu 20 Sep, 2007 13:08

If I assume your pool is 5 feet deep, then it's around 17,000 gallons. I don't know the size of the bags of TurboShock you used, but if I assume 1 pound and that these are 75% available chlorine, then 3 bags (pounds) would increase the FC level by about 16 ppm.

To shock your pool to kill green algae relatively quickly at a CYA level of 60 ppm requires a constant FC level of 24 ppm. This takes a lot more chlorine than you have been adding since the chlorine will get consumed by algae. You don't just add chlorine once and then stop. You add it several times a day, if necessary, to maintain the high chlorine level.

Now it is possible that the green is copper instead, but it's more likely to be algae. You can take a bucket of pool water that is thickest with the algae and add some chlorine (even bleach) directly to the bucket of pool water. If the green turns gray, then it's algae for sure (copper won't change in color and may even darken at the higher pH from adding bleach). You could add TurboShock to the bucket instead of bleach, but the high calcium and pH may lead to cloudiness which will make it harder to see if the algae changes color.

To test high chlorine levels, you will need a FAS-DPD chlorine test kit such as the one found in the Taylor K-2006. If you already have a test kit that is drop-based (not test strips) for the other parameters, then you can just get the FAS-DPD chorine portion in the Taylor K-1515-A as shown here . Regular OTO and DPD test kits will not distinguish above 5 ppm FC and the DPD test kit will actually wash out above 10 ppm FC.

Richard

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