CYA question, please help


Well-known member
May 18, 2010
I drained my pool water according to the % (43) the pool calculator said to decrease the salt in my water. It was way over.

I did complete set of tests this morning before I went to pool calculator and added anything back.

1) I did CYA test in the sunlight with the sun to my back as I read from someone's post here. With that light it was 70. I noticed as I walked to the table that the black dot was still there when I stepped into the shade, so out of curiosity I kept adding and the black dot didn't disappear until the reading was 50 in the shade. Which is more accurate?

2) Copper measured at 0.1 or 0.2. That's basically nothing with most things. Is that still the case with copper or is it so damaging that even that small amount is not good?

FC 4
CC 0
TC 4
pH 7.5
TA 150 always high
CH 360 should I do something to lower this or I don't need to worry about it?
CYA 70 sunlight 50 shade
Salt 3380 yay!

Thank you. Oh, it hit about 109 degrees here yesterday. I read that a fountain will keep water cooler. Is there something you would suggest for my pool? It seems large to me, but it is very small in comparison to most of yours.


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
The CYA test is pretty hard to get used to at first. For now, call it 60. The next time you do the test, stay in the same lighting (backto the sun) and try to be consistent. When I started, I got other peoples opinion and sorta' arrived at a consensus.

The test itself is only accurate +or- 10ppm, anyway, so your pool might really be at 60.


LifeTime Supporter
Jan 11, 2009
Cupertino, CA
I've also heard that a fountain can cool the water, but I have no personal experience with that. Running the pump at night might help a little. Running a fountain will also likely cause your pH to increase. But that isn't really a bad thing, because then you'll need to add acid, which will also help lower your TA.

CH 360 isn't really bad (it's about where mine is) but if you have significant CH in your fill water, it will keep going up. Lower TA some and keep pH around 7.5, it shouldn't be a problem.

Sorry I don't know what a good or bad copper level is.

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