Testing CYA with standard solution

lefty51 · Jun 11, 2015

I realize I'm probably over thinking this (or I just need longer arms) But.... I have been coming up with a CYA reading of about 60 and was debating raising it. Instead I said lets do it the right way.
So I received my CYA, CH, and TA reference solutions today. (very fast shipping, Thanks Dave!)
Anyway , just finished doing the CYA test and I'm coming up with 40 on the reference instead of 50. I know my old eyes aren't that good.

Given the narrow parameters with SWG, I'm stuck with thinking if 50 looks like 40 to me, than maybe my pool reading that looks like 60 to me is really 70.

Ohhh.... my head hurts, where is chem geek when I need him ? :scratch:

chem geek · Jun 11, 2015

The lighting conditions make a big difference in the CYA test. If you are reading lower, then you might have more direct light hitting the tube. The test is designed to use strong indirect light so standing outside with your back to the sun where your body is shading the tube and you are looking straight down into it in front of you holding it just above your waist. If you still get 40 ppm, then you should just figure your real CYA is somewhat higher than what you measure.

Richard320 · Jun 11, 2015

Those graduations aren't equidistant, so adding 10 to compensate doesn't quite work. What you need to do is find the right combination so you DO see 50.

For me, it's standing on the patio in full sun so I get all the light reflecting off the concrete, holding the tube with just thumb and one finger because more fingers than that blocks too much light, at waist height, and turned so the sun doesn't create glare on the surface of the water in the view tube. It's tempting for us oldsters to move it into bifocal range but that messes with my results.

lefty51 · Jun 11, 2015

Thanks fellas, I know I'm close on my reading, but it drives me batty

I read a lot of the previous posts about using the R-7065. I've been testing with sun at my back (holding with thumb and finger at the top like you suggested). I am curious though, when I'm looking down the sun shining between my legs is visible, could that be it. Maybe I should wear a long skirt

The neighbors are far enough away I don't think they would notice. Anyway I have a new bottle of R-0013 and I will hunt until I find the sweet spot where I can get a 50, then go from there. (geez, 50..... that seems so long ago

) I WILL conquer this, I own my CYA, my CYA doesn't own me ! :whip:

Snoufette · Jun 21, 2015

I am having the same problem. It's driving me crazy. Here is a pic of my standard solution with reagent and following all instructions I've read on this site. It's measured in the tube to the 50 ppm line. The black dot is not one bit obscured in my opinion. Am I crazy? I created my own thread on this matter and most responses say I'm doing something wrong but I am not!!!!

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chem geek · Jun 21, 2015

That's not obscured. Are you sure you mixed and waiting long enough -- 30 seconds?

If the CYA standard solution is correct, then maybe there's something wrong with the melamine solution not being concentrated enough or at a low enough pH. There's another report of errors very similar to this (i.e. reading too low) in this thread though there it appears to be a difference in the viewing tube (or possibly the mixing bottle).

Dave, you should try this with the same melamine solution lot and see if you are seeing this problem with CYA Standard Solution. If so, then contact Taylor about the melamine solution. You should also check the pH of that solution -- it should be quite low (you'll need wider range pH paper to test it -- the pH should be 2 or so, I think).

Snoufette · Jun 22, 2015

chem geek said:
That's not obscured. Are you sure you mixed and waiting long enough -- 30 seconds?

If the CYA standard solution is correct, then maybe there's something wrong with the melamine solution not being concentrated enough or at a low enough pH. There's another report of errors very similar to this (i.e. reading too low) in this thread though there it appears to be a difference in the viewing tube (or possibly the mixing bottle).

Dave, you should try this with the same melamine solution lot and see if you are seeing this problem with CYA Standard Solution. If so, then contact Taylor about the melamine solution. You should also check the pH of that solution -- it should be quite low (you'll need wider range pH paper to test it -- the pH should be 2 or so, I think).

Yes I wait at least 30 seconds. I've done the test several times and followed the extended instructions on this site.

duraleigh · Jun 22, 2015

I am in contact with both Snoufette and Lefty51 to see what the issue(s) might be.

We tested the current batch we are now shipping and it tested an average of 47.5 (50, 50 and 45 ppm by three folks, all of whom have done the test before so it appears what we have is fine. I'll report back as soon as I find out some info from these two members.

chem geek · Jun 22, 2015

I just did a test with the solutions that I have and it's right on where 50 ppm is obscured, 60 ppm I can faintly see the black dot, 40 ppm is also obscured, but I have older reagent and standard solution. This post shows some photos of the test with a 50 ppm standard at the 50,60,70 line.