CYA, FC and CC/TC

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PullJunkie

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Oct 7, 2018
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I am in the process of balancing everything to convert to SWCG. I have high CYA at 108. I am usually adding about 2.5-3 cups of 10% liquid chlorine daily to keep my levels between 1-3. My TC (CC?) is 2.28 and FC was 1.91 a few hours after adding 2 1/2 cups of chlorine this morning. I am using a Pool Lab 1.0 photometer for testing.

I believe I need to drain some water and replace with fresh to get my CYA to a good level. Is the high CYA the reason for TC being 2.28 and also for adding so much chlorine each day?

Otherwise, the pool is crystal clear with no other issues. ALK and PH are in spec.
 
The Pool Lab has been spot on so far when compared to other Hanna instruments and test kits that I also use to compare results. However, I, like you, am surprised I have no algae issues but it's been clean and clear for almost two months now. Pic attached. Would you agree I need to drain water, get the CYA down and my TC will fall in line as well?
 

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I don't have the Taylor kit but if you let me know if there's a specific model you use, I will get it and do a comparo. However the Pool Lab matches the results I get from the following: Blue Devil CYA test, the AquaChek with TruTest strips, a Hanna Ph Checker, Hanna Alkalinity checker and various generic strips. Yes I know strips are unreliable. It's just much easier for me to use the Pool Lab because it does everything in one with different reagents and zeros with each test. But that is here nor there. My CYA shows high in various tests and I believe I need to drain some water. Just looking for confirmation that would be why my TC is high I add alot of chlorine daily.
 
bonsey said:
I don't have the Taylor kit but if you let me know if there's a specific model you use, I will get it and do a comparo. However the Pool Lab matches the results I get from the following: Blue Devil CYA test, the AquaChek with TruTest strips, a Hanna Ph Checker, Hanna Alkalinity checker and various generic strips. Yes I know strips are unreliable. It's just much easier for me to use the Pool Lab because it does everything in one with different reagents and zeros with each test. But that is here nor there. My CYA shows high in various tests and I believe I need to drain some water. Just looking for confirmation that would be why my TC is high I add alot of chlorine daily.
Click to expand...

tillmac62 has given you a link to the recommended test kits. If your CYA is really 108, it's too high. With a CYA of 108, you need your FC to be ~9 to 13 to be effective. You need to replace some water to lower your CYA.

FC + CC = TC. From Pool School (see ABC's of Pool Water Chemistry - Trouble Free Pool): "Combined chlorine is an intermediate breakdown product created in the process of sanitizing the pool. CC causes the “chlorine” smell many people associate with chlorine pools. If CC is above 0.5ppm, you should SLAM your pool. CC indicates that there is something in the water that the FC is in the process of breaking down. In an outdoor pool, CC will normally stay at or near zero as long as you maintain an appropriate FC level and the pool gets some direct sunlight."

I would dump the Pool Lab and go with a Taylor based test kit.
 
Thanks. So I was confusing CC and TC. My CC is .37 (TC (2.28) minus my FC (1.91) according to instrument documentation). So CC looks to be in spec as well. Only issue thus far is high CYA at 108. I will get a Taylor kit to try as well but at this point I need to dump some water and get a new load to lower CYA.
 
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