Green pool

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.

Green pool

Postby dkohio » Wed 27 Jun, 2007 20:14

I have 30000 gal inground pool. In the past three weeks I have dumped 24 gal of hypo 15lbs of granular shock changed the sand in the filter but still have light green pool. The Cl2 is well over 10ppm enough to kill the algee.
All parameters are within the normal range except the pH 6.8. Iwas told the hypo would raise my pH but it has not. I run my pump 24/7.
Should I add pH increaser to get the hypo to work?

chem geek
Pool Industry Leader
Pool Industry Leader
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Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Postby chem geek » Wed 27 Jun, 2007 20:25

What is your Cyanuric Acid (CYA) level? 10 ppm Free Chlorine (FC) is not enough to shock a pool to clear it of algae if the CYA is high. Also, one must maintain the high FC level since it will get consumed (used up) by the algae. If there's a lot of algae, then vacuum to waste may be needed, brushing the walls, using a skimmer sock, and backwashing your sand filter (changing sand is not usually needed). You can also add a small amount of DE to the sand filter (add a small amount to the skimmer until the filter pressure goes up 1-2 PSI) which makes it more effective at clearing algae (the DE gets removed at next backwash). In the worst case if the pool does not clear and remains cloudy (you're not there yet), you can use OMNI Liquid Floc Plus -- but first you need to kill the algae as your pool is still green.

Also, adding chlorine only makes the pH go up temporarily as the FC level goes up. When the FC drops as the chlorine gets used up, the pH drops back down. When the FC is high, the pH test is not valid because the high chlorine level bleaches out one of the two components in the pH test.

It does not sound like you are getting accurate advice from your pool store. I suggest you get yourself a good test kit, the Taylor K-2006, and do the testing yourself and post your numbers so we can help you. In the meantime, if the pool store has given you a set of numbers for pH, Total Alkalinity (TA), Calcium Hardness (CH) and Cyanuric Acid (CYA), then please post them. Also, let us know if your inground pool is vinyl or plaster/gunite.

Postby Guest » Wed 27 Jun, 2007 21:21

I have a vinyl liner, ph 6.8 Ta 164, total cl2 10.6 fc 8.2 cya 50

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