CYA Standard Test Pics - Which is the result?

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When I did my CYA test of the known 50, I did the following:
  1. Taylor K-2006 tester
  2. Outside at 10am in the morning
  3. Clear bright day with sun at my back
  4. Test container on bar approximately waist height. (I did not hold the test container)
  5. Back to the sun with shadow of body on test container.
  6. Added solution until I could move my head from side to side and not make out black dot.
  7. Test showed 50.

With that said, I am in total agreement with everyone here. This test should NOT be that hard. I mean what are the chances that I will get exactly the same light every time I test? So what I learned today is that if the light is a little bit different, it could cause your testing to be off as much as 20ppm. That is huge!

I currently test once a week for CYA. What I am going to do is test the Known 50 first each time to ensure I have a good light, and then test my water. This will hopefully keep me from messing up too bad.
 
The known 50 sample does help, for sure. I do find that I can read CYA very accurately from 30-60 or so, it is very accurate for me. Where things start to get tougher is around 70-90 because the lines are so close together. I wish there was a tube for just the 60-100 levels
 
This is discouraging. I'm ready to take a sample to the dreaded pool store and see what they say the CYA is. I've been reading mine at the L 2 to L 1 visual and getting 60-70. I hate to think it's closer to 100. Although, that would explain why I have algae with a FC of 10! ?
 
This confirms my suspicion that the CYA test is wildly inaccurate and someone needs to come up with a better test.
 
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Please do not go to the pool store...you may be off 20 ppm - okay that is something, but the pool store may be off 20 or 50 or ?? I want definitive results too, it is our nature that's why we bought the kit but not the pool store! ;)

Testing it in the shade will cause the dot to disappear later aka giving a lower than actual read. Same as placing vial on a table to test blocking light from hitting the tube from the bottom. The CYA reagent, when hit with sunlight, decreases in transparency thus blocking the dot. As an experiment, test under ideal conditions then pour the solution back into the bottle to retest. But this time try it indoors, under a tree, etc. I think it was once explained that the 50 ppm standard should used to calibrate your test location and process to produce the environment to get the 50 ppm right. Then to use similar conditions to test in.
 
mgmoore7 said:
I just bought the "Replacement Comparator #9056", it has a higher OTO FC test than what came with my TF-100. I run my FC higher than 5, so this will save on FAS/DPD reagents and save a little time.
Click to expand...
The 9056 comparator is for DPD testing, not OTO.

I just use my FAS/DPD for daily testing. I will usually go through two 2oz bottles of R-871, and two 10g R-870 powder for the season (for about the price of the #9056 I can buy 10g of the R-870), $33 or about $6-7 a month over the season.

I figure at that cost why complicate things with two tests?

Dom
 
Ok, here's another set of pics. The first two columns are from a new test, with the View Tube "frosted" with Scotch tape. Column one is with the sample exposed to the sun, column two is with the sample shaded. Also, the camera was set a little higher today: 55cm (~21.5in) from camera to bottom of the View Tube, vs only about 40cm (~15.75in) yesterday (the inside pics w/a clear tube).

(All tests pictured below are of the 50ppm standard.)

50ppmSTD.frosted.sun-shade-inside.tfp.jpg

Picture taking protocol:
Fill tube to 100 with test water,
take pick in full sun,
shade the test area,
take that pic,
fill tube to 80...

It took about 4 minutes (avg 23 seconds per level) to take a complete set of "sun & shade" pics (not counting the empty tube pics).

The inside pics are from the previous day's tests, as I had to mix a new standard sample for the outside pics (spilled the first sample).

Ideally, a complete comparison would use the same sample thru-out, and include 6 scenarios:
a clear tube inside, outside in the sun, and outside shaded; then again with a "frosted" tube. I am considering doing all that for my doctoral thesis, but I haven't found a sponsor. Nor have I completed my master's degree. Or even a bachler's. But, it could happen!

Anyway, in the interest of full disclosure - the following assumptions were made:
I mixed the first test sample accurately...
I mixed the next days test sample accurately...
I didn't make any mistakes...
Everything went perfectly...
We ingore any other assumptions...
That the changing inclination of the sun during the 4 minute data collection protocol didn't unduly affect the refraction & subsequent photonic scatter in the test solutions...

One other minor consideration - the CYA/reagent does "clump up" over time. That is, if the solution is left undisturbed, it starts to get "grainier" over time. I noticed this the next day (I had saved the two test solutions). But I don't know if the 4 minutes of the above tests are enough for the results to be adversely affected by that change. It wouldn't be hard to test - fill to 50, observe, wait 4 minutes, observe again. Maybe another time, for now I'm going to go ride my bike for a few hours in the FL mid-day sun so I have a reason to jump in my pool when I get back...

Regardless, I think this little study still has merit. I think the take-away, as mentioned already upthread, is to test your CYA standard in a known & repeatable lighting situation & a consistant height (eyes to tube), note what it looks like when filled to the 50ppm line, and use that as a point of reference for all subsequent tests of pool samples. And don't waste as much time as I just did - just get in & swim!
 
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after reading this thread I'm kinda thinking my CYA of test of 85ish is probably closer to 100. Which would explain why I would see a bit of algae on my steps with a FC of 9 and I'm running it 12-14 with no algae. Kinda went a bit overboard with the CYA early this season, oops.
 

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Technobuyer said:
Pardon my ignorance.. How are ya'll using the replacement 9056 block to measure CYA? Is there a dot on the bottom of one of the vials?
Click to expand...
Yes
e0bbf94655b1c243a854e3c0b77533a1.jpg
0123731f2eb91ebe7e12abc8512c8e66.jpg


Sent from my 6045O using Tapatalk
 
LittleTagAlong said:
Where do you get the standard? I see several places, but it's all 13 oz or larger. I don't need that much
Click to expand...

The TF-100 test kits now contain the standard, and that's where I got mine. I'm not sure where else to get it.

However, if you have a very precise scale, you could potentially make some - just do the math to add a known amount of CYA to a proportionally known amount of plain/distilled water. (I have no such scale, and probably would mess up the math...)
 
I have the Taylor R - 004 reagent for pH, but I don't have the corresponding comparator.

Can I use the 9056 block to measure pH?

Actually, the block comparator that I prefer is the 9058, the one with the CYA scale
 
They both have the CYA scale. The one with the pink color matching blocks is used with the K-1001 reagents (R-0001 & R-0002) for doing DPD-only color testing of FC.
 
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