Test CYA in the sun or shade?

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J

johnvk

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Jul 1, 2015
13
New Jersey, USA
I was testing my CYA today. It's been low all season, and i've been chlorinating with trichlor to raise it. And it's been cloudy a lot, and i'm not needing a lot of trichlor so it's taking a while.

Anyway, i am getting close on my CYA. I was testing it, in the shade, under an umbrella, and it was 40. Good, i thought.

But i also thought, wait a minute, i'm testing how light passes through a cloudy solution, and if there was more light, more light would get through.

So, i walked into the sun. Sure enough, i could now see the dot at the bottom. I kept pouring the solution in til i could not see the dot--in the sun--and it now read 30.

So, which is accurate? In the sun or the shade?

BTW, i dont have the trouble-free-pool test kit. I have the taylor test kit, purchased at leslie's pools. It has chlorine with a 2step 5-drop process for free CL, and another reagent for combined CL. And it has ph, the cya test, and TA and Calcium Hardness. Taylor calls my CYA reagent "r13", if that helps. Sounds like the same directions as the TF-test kit.
 
Welcome to TFP! :wave:

You want to test in strong indirect light and the best way to do that is to stand outside with your back to the sun with your body shading the tube in front of you that you hold about waist-high looking down straight into the tube. You do not want any direct sunlight hitting the tube.

Your 40 ppm reading was probably the accurate one. Note that you can pour back and forth from the mixing bottle to the tube if you think you missed where the dot just disappears.

As for test kits, you have the Leslie's re-branded equivalent of the Taylor K-2005. What you are missing is the FAS-DPD chlorine test and you can get that at TFTestkits. It will not only be more accurate, but will let you test high FC levels if you ever need to SLAM your pool.
 
wow my post and your reply both got in before forumaggedon tonight at 12 cdt ;)

as for the CYA...you're so sure! How do you know this? Is there some standard for ambient light or something? So interesting!

And i guess this means you can't test CYA (using this test) on a cloudy day lol ;)

It was actually 35 in the sun (i checked my record). So now even more the 40 is probably right.

Thanks so much!
 
I called or E-mailed (I don't remember which) Taylor Technologies a while back and asked them how they standardized their test. They recommended the strong indirect lighting and the sun to one's back. I have since compared the CYA test to CYA Standard Solution and found that the technique gave the most accurate result for that standard.

You can still test CYA on a cloudy day since it's still strong indirect light if it's light white clouds -- basically the clouds are doing the "shading" for you -- but if it's dark clouds then that would be too dim. What doesn't work so well is doing the test indoors unless you have some rather strong lighting but do not hold the tube directly in sight of a bright light. It is very, very rare for indoor lighting in a home to be as bright as outdoor indirect light.

Very roughly speaking, direct overhead sunlight is around 100,000 lux, strong indirect light (i.e. shaded from the sun) is around 10,000 lux, an overcast sky is around 1000-5000 lux but varies on how overcast (which is why a bright white cloud overcast is still OK), indoors is usually < 1000 even in a bright kitchen (more typically 500 lux).
 
I really have a problem with the CYA test....I have the K2006 kit, so I ordered from TFTtestkits the larger CYA tube & mixing bottle. ordered the CYA standard 50 solution, 16oz of the R-0013 CYA and went to work.

With the standard 50 solution, I can see the dot all the way to 30.....with my pool water I still guess at my readings from 120-160 (I mix 50/50 because I do know it is high)....but I really have problems with this test.

I have tried back to sun, in the sun, slight shade, under patio, next to side of house, standing, sitting, with a cap on, without a cap, with my glasses on, with my glasses off, almost everywhere.

I did find the easiest way to see the dot, in a bright sunny day with no clouds, just inside my patio where the shade starts looking into the tube I have the best view and the lowest 'best guess-estimate' CYA readings.....with my back to the sun with light surrounding you everywhere is the hardest to see the dot and I get my highest 'best guess-estimate' CYA readings.
 
Duplicate of this post in another thread. Please only post in one thread or if you want to reference your post (as I have via a link) then you can do so. The issue of not matching a standard discussed in the other thread is a separate one from the proper way of viewing discussed in this thread.
 
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