CYA quandry

[mariane]

I have been testing the CYA levels of the pool water in several conditions and each time have gotten a different number.
On a cloudy day: 35
In shade: 40
In full sun with the sun at my back: 50
I'm interested in why this happens and in which condition is best to test CYA.
Thanks for your help.

 

[RobbieH]

full sun with sun to your back.

Pool School - CYA

Stand outdoors with your back to the sun and hold the view tube at about waist level. If sunlight is not available, find the brightest artificial light you can.

 

[mikemass]

I find the CYA test to be very subjective as to determining exactly when the black dot "disappears". I have the same issues in any light.

 

[RobbieH]

Here's the main thing. Are you in the 30-40 range, or 70-80. See what I mean?

 

[Frankhugus]

I find the CYA test to be very subjective as to determining exactly when the black dot "disappears". I have the same issues in any light.

Me too. Having high CYA I want to keep "seeing" the dot and that might influence the result.

 

[mariane]

Thanks RobbieH. In all the past threads I've read, the "shade" numbers should be higher than the "full sun" readings but mine are backwards.

We do a partial drain in the fall for the winter deep freeze and then refill in the spring. Our tap water does not have any CYA in it. Since full sun number is 50, and I have not added any CYA this year, the levels must have been very high last year which I don't remember that being the case.

That would explain the SLAM taking longer than usual. I was going by the "35" reading and still have slightly cloudy water. The FC levels drop 4 numbers every night.

 

[JoyfulNoise]

Full sun, tube waist high in the shadow cast by your body. You MUST make sure that your hand is in no way blocking the frosted plastic of the tube. If you are using the K-2006 with the large block comparator then you hold the block by the pH side. If you are using the narrow tube with the TF-100, then you "pinch" the top of the tube between two fingers and keep your hand and fingers flat and extended (like how to hold a cup of tea in proper British royalty fashion). Also, as you add drops, try to look away every so often to relax you eyes - staring intently into the tube can make the dot appear to be there. As well, keep the tube vertical - the curvature of the water at the meniscus can make the dot seem to be there.

 

[mikemass]

I don't "pinch" the tube. I place it on a white piece of paper and let it stand on it's own. Is this wrong?

 

[lindaspoolboy]

i use this:
TFTestkits.net (R-7065 CYA Standard Solution)
to help develop a gut feel for what it means for the black dot to "disappear".

 

[JoyfulNoise]

I don't "pinch" the tube. I place it on a white piece of paper and let it stand on it's own. Is this wrong?

No. As long as you maintain a good eye-tube distance and the lighting is bright and indirect.

i use this:
TFTestkits.net (R-7065 CYA Standard Solution)
to help develop a gut feel for what it means for the black dot to "disappear".

New TF-100 kits will now be sold with a small amount of that standard solution to help new TFP users get used to the test.

 

[mikemass]

I got to get some of that R-7065 to see what it really should look like. Thanks for that.