pool algie

[pcaman]

my problem is what looks like dirt in the bottom of my above ground pool. when I brush it .it turns into green cloud and several hours later it is back. I have tried vacumeing with the same result. We use a sand filter, I test twice weekly shock every Fri. Have had the pool for four years and never had this issue. Any ideas.

[lbridges]

You have to test and know your chlorine level (free and combined, or FC and CC) as well as the CYA level.

You will have to shock until the algae is dead, but if you have been using pucks or dichlor granular, the amount of chlorine needed to shock might be sky high and that could explain why the shock you have been using is no longer effective.

[pacman]

Not sure what is ment by CYA levels. also what is free and combined. I use a system where you add drops and get to a certain color level one for PH the other for chlorine. is there a different test kit I should get. Thanks

[lbridges]

CYA is short for cyanuric Acid - also known as pool stabilizer. It is a major constituent of Trichlor and Dichlor. The problem is that it never goes away in pool water. Unless a user does partial drains (wintering), or has a lot of rain and lots of filter back-washing the CYA can build up requiring more and more chlorine to ever get to shock level.

A pool store ought to be able to tell you the number. Then you can determine how much chlorine to put in to get rid of algae.

A Chlorine/CYA chart exists here that shows how higher CYA levels impact the chlorine needed to maintain a clean pool, and/or shock.

Free chlorine is chlorine available to do what chlorine is supposed to do, sanitize the pool and the amount needed is ties up with the CYA number (above info). Combined chlorine is chlorine that has already found something and begun to oxidize it. A combined chlorine level much over 0.5PPM means the chlorine is fighting something in the pool.

[JBOY]

I blocked one end of a old spa cartridge filter hooked up the other end to vac. Hose and brushed the green cloud to the cartridge filter. Do a small section at a time by moveing the cartridge around the pool. Takes a few days to get it out. (take cartridge out and rinse off when it turns light green)

j boy