pool algae returns all season long

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

pool algae returns all season long

Postby cozmo1 » Tue 09 Sep, 2008 08:22

I have the same but different problem with my pool. For fifteen years I have always had crystal clear water. At the end of last year I had a slight algae problem that I thought I took care of right before I closed the pool by shocking it and adding algaecide before covering it. From the begining of this year I have had algae all year long. I have used over seventy pounds of chlorine tabs, sixty bags of shock, run sand cleaner through my filter. All of my readings seem fine, chlorine all year has been at around 5.0(high) PH is 7.4 alkalinity is 110ppm. Every three days I have to brush the bottom and sides of my pool as the algae keeps growing and getting worse. I let it go this past week as we went away and now that I'm back my pool which has a blue liner looks like a pond all green and you can't see five inches below the surface. My pool holds around 22,000 gallons.No one has been able to help. I don't know what else to do!

chem geek
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Postby chem geek » Tue 09 Sep, 2008 10:16

You say that all of your readings seem fine, but if you've been using lots of chlorine tabs then your CYA level may be very, very high. You will probably need to do a partial drain/refill to lower it. If your "shock" product was Dichlor, then the CYA is most certainly through the roof (if it was Cal-Hypo, then the Calcium Hardness may also be high, though that does not affect algae).

You should get yourself a good test kit. You can get the Taylor K-2006 for a good online price here or the TF100 test kit from tftestkits(dot)com here with the latter kit having 36% more volume of reagents so is comparably priced "per test".

To kill algae, you have to have the Free Chlorine (FC) level high enough relative to the Cyanuric Acid (CYA) level. If the CYA level is too high, then the FC will not be effective and won't be able to kill algae faster than it can reproduce. You can read more about defeating algae here.


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