My pool store indicates chemical levels are normal, yet pool is turquoise. I purchased a Taylor K-2006 test kit with the following results. Free Chlorine 3.0, Combined Chlorine .2, PH 7.4, Alkalinity 90, CYA 100, Calcium 100. I have a sand filter where I replaced the sand, and have had it running for 4 straight days. The pool started the season crystal clear, then suddenly turquoise. Any Help or Suggestions are appreciated.
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- Thread starter Ciarniello22
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I am sure our resident chemists will be along shortly, but I am thinking the CYA may be a bit high. Meanwhile you could click on the Pool School link at the top of the page and read up on the relationship of CYA to chlorine to get a better understanding of what needs to be adjusted.
Welcome to the forum. 
With a CYA of 100, your chlorine has been rendered pretty ineffective, allowing algae to grow in your pool.
The correct way to fix that is to drain 50% of your pool so your 100 CYA reading then becomes 50 (although your CYA may be higher than 100) and your pool will be manageable again. The SLAM process is next and your pool will be ready and crystal clear the rest of the season.
With a CYA of 100, your chlorine has been rendered pretty ineffective, allowing algae to grow in your pool.
The correct way to fix that is to drain 50% of your pool so your 100 CYA reading then becomes 50 (although your CYA may be higher than 100) and your pool will be manageable again. The SLAM process is next and your pool will be ready and crystal clear the rest of the season.
I am copying and pasting this from an other thread I replied to. Partial draining and re-filling is going to fix your high CYA for now, but it will go back up again if you keep using solid forms of chlorine.
To get a full understanding, re-read Pool School. However the key thing to understand is CYA and forms of chlorine.
Your pool needs CYA - it slows chlorine loss, but it also makes chlorine less effective. 50 where you are is fine (a touch high IMO, but still OK). You do not want it to go higher, or else you will start having problems. CYA does not drop on it's own, the only way to lower it is too drain some water and add fresh.
Now here comes the kicker - any kind of chlorine that you buy that comes in solid form - pucks, sticks, granules - either shock, tabs, clean and swim, or whatever else they call it, also contains CYA - that is just how it is. Using solid chlorine will raise your CYA.
That is why we say to use bleach (or, if you have a source and are comfortable with it, liquid chlorine, which is in essence stronger bleach)
To get a full understanding, re-read Pool School. However the key thing to understand is CYA and forms of chlorine.
Your pool needs CYA - it slows chlorine loss, but it also makes chlorine less effective. 50 where you are is fine (a touch high IMO, but still OK). You do not want it to go higher, or else you will start having problems. CYA does not drop on it's own, the only way to lower it is too drain some water and add fresh.
Now here comes the kicker - any kind of chlorine that you buy that comes in solid form - pucks, sticks, granules - either shock, tabs, clean and swim, or whatever else they call it, also contains CYA - that is just how it is. Using solid chlorine will raise your CYA.
That is why we say to use bleach (or, if you have a source and are comfortable with it, liquid chlorine, which is in essence stronger bleach)