CYA Site Tube Accuracy?

[Kylum]

Hello everyone,

New pool owner. Just received my TF100 and upon testing I noticed the large variance in reading through the site tube for CYA. Tested several times with three sets of eyeballs. I can still make the dot out to around 60 to 70 ish. My wife and son can’t see it as you approach 90. Now I have super vision and can spot nails in the road with enough time to avoid them so… Obviously, this test has room for error and I know that my levels are high (used pucks during last season before I found this site) but at what level should I go with?

When adding liquid chlorine I used 90 CYA since that was the point where I had to start focusing and was the point my family could not see it. Will be checking for cl2 residual loss in the A.M. to see if I need to SLAM but I don’t think I will have to since I haven’t added any before today cl2 in 8days and it only dropped 4ppm. I did have algae problems before closing last year so I’m going to make sure I’m on top of it before this season begins.

Thanks

 

[mknauss]

Welcome to the forum!
When you do the CYA test, try this next time.

Once you have your solution ready, back to the sun, etc. Fill the vial to a line, say 80, lower the vial to your waist level and glance for the dot, you see it, add solution to the 70 line, glance, see it, repeat until you no longer see it with a glance. Then use the CYA value one step above the line you read. So if you stopped at 50, use 60 ppm CYA.

The vial is in logarithmic scale. So it is not viable to interpolate between the lines. Just use the whole numbers, such as 50, 40, 30, ....

I suggest you read through Pool School - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

 

[Kylum]

Welcome to the forum!
When you do the CYA test, try this next time.

Once you have your solution ready, back to the sun, etc. Fill the vial to a line, say 80, lower the vial to your waist level and glance for the dot, you see it, add solution to the 70 line, glance, see it, repeat until you no longer see it with a glance. Then use the CYA value one step above the line you read. So if you stopped at 50, use 60 ppm CYA.

The vial is in logarithmic scale. So it is not viable to interpolate between the lines. Just use the whole numbers, such as 50, 40, 30, ....

I suggest you read through Pool School - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

Thanks for the fast reply. Makes sense and will redo the test tomorrow. However, I did pretty much what you stated and as per the TF-100 card provided in the kit. The only difference was “glance” which will definitely make a difference. I will continue reading through the pool school. Haven’t watched any videos yet but will do.

 

[flynwill]

When you say "back to the sun" should the vial be in your own shadow or in the direct sunlight?

 

[mknauss]

When you say "back to the sun" should the vial be in your own shadow or in the direct sunlight?

CYA - Cyanuric Acid Test

Cyanuric Acid (CYA) is the chemical name for what is commonly referred to as Stabilizer … Read more…

www.troublefreepool.com

4. 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.

 

[Jimrahbe]

Flyn,

I find that once the dot goes away, I can still see it, if that make any sense...

So, what works best for me, and for repeatability, is to stop when the dot "almost" goes away.

Kind of subjective, but if I do it that same way each time, I get the same results.

Thanks,

Jim R.

 

[flynwill]

4. 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.

I'm sorry but that doesn't answer the question: Is the intent of this direction to say that the tube itself should not be in the direct sunlight?

I'll admit I've tried viewing the tube under a variety of conditions and found very little variation in the visibility of the dot, so the directions to me seem just a little bit overstated. But I can easily believe that the result will be somewhat different if the tube is illuminated by point source (eg the sun) vs if it is illuminated by diffuse light (eg open shade).
-Will

 

[Toxophilite]

I think of it like the test to "stare at the dot" then look away. Still "see the dot"? So, I stop when I think it disappears, then I keep looking till I can't see the dot - it really disappears. I seem to get consistent reading, whether truly accurate or not, and my first time after getting kit matched my PS test and my even more subjective test strip.

 

[Dirk]

I set my test vial on a white piece of paper on my laundry room counter. I use a bright, indoor, LED, under-counter, strip light, that is 99% consistent from session to session. It's not subject, at all, to outdoor conditions or time: day, night, cloudy, sunny, morning, afternoon... doesn't matter. I use the test manufacturer's sample images to judge the dot. I don't glance, but rather take my time. This MO is not exactly what is taught most often here (the back-to-the-sun deal), but I feel consistent test conditions are important. Many folks here have great results with the TFP instructions. I've found what works best for me.

From this page:

Why Monitor Cyanuric Acid?

I use these images (notice the white background, and the diffused lighting, that's what I attempted to recreate):

 

[Dirk]

FYI: once you've completed the CYA test, you can pour the mixture from the test vial back into the squirt bottle and repeat the test, pretty much as many times as you like. I always do it at least twice, sometimes three or four times.

 

[aussieta]

i do the cya test mid morning or mid afternoon
so the vial is in my shadow
i fill to 100 and hold vial at waist and have a quick glance
if i see the dot i fill to the next line and repeat
if you stare at the dot you will keep seeing it

 

[newdude]

I'm sorry but that doesn't answer the question: Is the intent of this direction to say that the tube itself should not be in the direct sunlight?

Correct. Hold it at your proverbial belt buckle and take a super quick glance down. If you see it at that first glance, fill 10 more and try again. Like @Dirk said, suck the mixture back up and do it as many times as you need. I liked to get 2 out of 3 that agreed before being happy.

 

[Kylum]

Great feedback and tips on getting the most accuracy possible. After testing again and only doing a “glance” it looks like I landed at 80 that is very repeatable after multiple attempts. Drained the pool half way and it’s filling back up as I type. I’m feeling confident that this year will be prove better than last year thanks to this forum and the tools/ knowledge the community provides!

 

[newdude]

I’m feeling confident that this year will be prove better than last year thanks to this forum and the tools/ knowledge the community provides!

I am entirely confident. we got you now.

This will be you.

 

[JoeSelf]

I'm sorry but that doesn't answer the question: Is the intent of this direction to say that the tube itself should not be in the direct sunlight?

I'll admit I've tried viewing the tube under a variety of conditions and found very little variation in the visibility of the dot, so the directions to me seem just a little bit overstated. But I can easily believe that the result will be somewhat different if the tube is illuminated by point source (eg the sun) vs if it is illuminated by diffuse light (eg open shade).
-Will

The tube should be in the shadow of your body..