Anyone ever do a controlled experiment on the CYA test?

[wayner]

IMO this test is very hard and must have a large margin of error. This test could be affected by ambient light, how far you hold the tube, the quality of your eyesight and other factors.

I would love to see 10 people given the exact same water with a CYA level of 40 and see what they get for the level. I would bet that the dispersion would be very large.

 

[Jimrahbe]

W,

In my mind accuracy is not a big deal in the CYA test. In the big picture you are really only interested in a couple of points..

1. Do you have any CYA at all?

2. Is it over 100?

3. About where is it between zero and 100?

If you are off by 10 ppm either way, it does not have any major impact on your pool care.

The next thing is if you just do it the same way every time, then even if your reading is off from the 'actual' CYA level, you will still see the same results every time. I have in my mind the way the dot should look where I stop the test. Finding the exact point where the dot disappears altogether is impossible for me to do.

Thanks,

Jim R.

 

[wayner]

Ok thanks. I find that I have to add lots of CYA every spring after opening my pool. I always struggle with "can I still kind of see the dot" - I am guessing that my initial reading was 35. But I am kind of getting a feel for how much to add. So far I have added 3.5kg of granular CYA, which will hopefully be enough. My pool is about 100,000 litres.

By the way, does temperature affect this test? My water is currently very cold at 57F.

 

[bljamison]

I understand about the disappearing dot thing. I try to keep my CYA at around 30ish. If it appears I'm filling the entire tube and can still barely see it, I might need some, and if I do, I just use a couple of pucks for a week or so and it will come up slightly. I quit fooling around with trying to dissolve the granulated CYA and why waste $$ purchasing it when I try to have some pucks on-hand for this, or if I go on vacation or something and can't tend to my pool. It works for me.
I sure learned the first year when I didn't know anything and was trying to learn everything. The pool builder put in pucks and what I was reading online said to use them so I thought I was doing good until CYA shot up. Once I stumbled onto this site, and another article that talked about the correlation between pucks and CYA rising, I was kind of irritated that the pool builder, who also has a store, didn't seem to worry about it.

 

[Jimrahbe]

By the way, does temperature affect this test? My water is currently very cold at 57F.

W,

Water temp effects my salt tests, but I don't think it effects the CYA test.

Keep in mind that I don't check by CYA until after my water has warmed up enough to allow my salt cell to work. Usually in the 60's...

In fact what triggers me to test my CYA is if my salt cell has to be set higher than normal to maintain the FC I want. When that happens it is almost always because my CYA is too low.

I guess my point is that I adjust my CYA to allow my pool to work the way I want vs. trying to have my CYA be a specific number.

Thanks,

Jim R.

 

[kimkats]

There is a CYA solution that is said to be 50 cya. That might help you a bit.

 

[Bperry]

Ok thanks. I find that I have to add lots of CYA every spring after opening my pool. I always struggle with "can I still kind of see the dot" - I am guessing that my initial reading was 35. But I am kind of getting a feel for how much to add. So far I have added 3.5kg of granular CYA, which will hopefully be enough. My pool is about 100,000 litres.

By the way, does temperature affect this test? My water is currently very cold at 57F.

The CYA test should be above ambient temperature as cold water affects it according the the TFP folks.

 

[JamesW]

Questions In Our Pool/Spa Mailbag

Do pool or spa water samples have to be at "room temperature" before testing begins?

For consistency, reliability, and accuracy, we recommend sample temperatures to be between 50-90℉. Sample temperatures <50℉ or >90℉ may produce unexpected color development.

 

[JamesW]

"Yes…it’s cold…VERY COLD…especially out here on the East Coast. Record low temps, blizzards, and runs on the grocery store for bread, milk, and toilet paper (inside joke for us in the Baltimore area) make this such a “special” time of the year.

Brrrrrrr… As a result, this frigid weather has led to a barrage of calls and e-mails about testing pool/spa water with low temps. Imagine that! Seriously though, low temps can affect test results, reaction times, solubility within the sample, and reagent efficacy.

For example, it may take a few more drops of reagent in a total alkalinity or calcium hardness drop test before you see the color change, which will result in a false-high reading.

In a pH test, some reagent components may precipitate when the reagent is added to a low-temp sample, causing faded test colors, inaccurate results, and/or no reactions at all!

It’s also widely known that CYA testing of low-temp water will provide false-low test results (even at water temperatures in the 60s) because the speed in which the precipitate forms is slowed down tremendously.

Other tests could be affected as well.

For test strip users, be aware that temperatures <45°F (7.2°C) can affect color development.

And for those of you who use meters, you’ll be happy to know that low-temperature samples do not usually affect test results, but it would be wise to verify this by checking your meter’s specifications.

As a general guideline, we recommend not testing pool/spa water samples that are <45°F (7.2°C).

Another important reminder: Store reagents and test kits in a temperature range of 36°F–85°F (2.2°C–29°C).

So, what’s the “get around”? If you must test pool/spa water <45°F (7.2°C), collect the sample from 18″ below the surface (again…brrrrrrr!) in an opaque container, bring it inside to a warmer environment, and wait a few minutes before performing the test. Remember…patience is a virtue!"

https://www.taylortechnologies.com/...d-temperatures-affect-your-poolspa-water--733

 

[JamesW]

Standard Solutions

tftestkits.net

 

[wayner]

Do pool or spa water samples have to be at "room temperature" before testing begins?

For consistency, reliability, and accuracy, we recommend sample temperatures to be between 50-90℉. Sample temperatures <50℉ or >90℉ may produce unexpected color development.

To change the subject for a second, this would imply that you should let spa samples cool off a bit before testing. My spa is set at 102.

 

[JamesW]

To change the subject for a second, this would imply that you should let spa samples cool off a bit before testing. My spa is set at 102.

That is from Taylor.

You can contact them to see what they say.

https://www.taylortechnologies.com/en/content/contact-technical-support

https://www.taylortechnologies.com/en/content/contact-customer-service

 

[Thurston]

It's the worst! And I've found the instructions and forum advice to be inconsistent and adding to the frustration of a very difficult and flawed test:

Cya and fc are the most important factors to a chlorine balanced pool...but the test is plus or minus 20 and it doesn't matter as long as it's not over 100. Now add exactly this much chlorine based on the results, not too much or it will damage your liner, bit too little or you get a swamp. But no problem! Just slam based on the same test. Look at the dot, when it disappears take a reading. The dot should be completely gone...or maybe still visible but just barely...or maybe visible but with edges "a little blurry". Make sure it's read with your back to the sun, but not sunny, cloudy. Now look at these 5 pictures of what it should look like from 5 different people that are all different. Still confused? Order a bottle of this standard, perfectly 50 ppm cya water and rest it to "calibrate yourself". Then struggle to see the dot past a reading of 70.

Easy!

 

[Newdude]

adding to the frustration of a very difficult and flawed test:

It gets us all, I promise. And we all have our own way that we were able to justify it to ourselves.

My way ? I fill to the 10s only. It's much easier to tell its not a 40 or a 60 so it must be a 50. I do best of 3 and if I'm off by 10 because i should have rounded up this time, that's within the acceptable variance.

 

[RickRude]

There is a CYA solution that is said to be 50 cya.

Emphasis added.

Why are you injecting doubt into the veracity of the standard solution? I bought some last year, and nailed 50 ppm. But I did my test indoors in a windowless room which is contrary to most of the guidance here...so now you have me doubting myself.

 

[Bperry]

Emphasis added.

Why are you injecting doubt into the veracity of the standard solution? I bought some last year, and nailed 50 ppm. But I did my test indoors in a windowless room which is contrary to most of the guidance here...so now you have me doubting myself.

It’s a some what subjective, imperfect test, that doesn’t really matter one way or the other if you read 20ppm higher or lower than reality. Close enough is good enough in this case.

 

[Rocket J Squirrel]

Why are you injecting doubt into the veracity of the standard solution? I bought some last year, and nailed 50 ppm. But I did my test indoors in a windowless room which is contrary to most of the guidance here...so now you have me doubting myself.

Interesting. The last time I tested with the standard solution, I had to hold the tube in full sun for it to read 50. In shadow, it read 70.

 

[Methuselah]

There's probably a few work-arounds to get more accuracy.

For me, I do the testing and let the pool store also, if they somewhat agree I go with that. It's the one test that using their equipment is likely the more accurate way to test (if they use an electronic and calibrated comparitor system).

I'm guessing if you bought several of the standard solution samples they would all test different anyway

Best bet though, is when you dump, keep an account of how much you put in there and do the math. Of course this is on a hot tub, does you no good in a pool.

All that said, here's my suggestion to those "inclined" electronics hobbyist types. Get some standard solution, set up (make) an optical comparitor system to fit in a container that can be closed, and adjust it so the level just trips at the right point on it. At least that can be used to check a cheap meter (until calibration drift gets you...) or allow a comparison to the local pool store.

FWIW, I seem to recall most of my measurements matching what I weighed when I put it in there, and the pool store was close too. But yeah, testing ucks.

Always long-winded, sorry.

 

[Bperry]

There's probably a few work-arounds to get more accuracy.

For me, I do the testing and let the pool store also, if they somewhat agree I go with that. It's the one test that using their equipment is likely the more accurate way to test (if they use an electronic and calibrated comparitor system).

I'm guessing if you bought several of the standard solution samples they would all test different anyway

Best bet though, is when you dump, keep an account of how much you put in there and do the math. Of course this is on a hot tub, does you no good in a pool.

All that said, here's my suggestion to those "inclined" electronics hobbyist types. Get some standard solution, set up (make) an optical comparitor system to fit in a container that can be closed, and adjust it so the level just trips at the right point on it. At least that can be used to check a cheap meter (until calibration drift gets you...) or allow a comparison to the local pool store.

FWIW, I seem to recall most of my measurements matching what I weighed when I put it in there, and the pool store was close too. But yeah, testing ucks.

Always long-winded, sorry.

Actually the CYA test is the one pool stores get wrong the most based on searching threads on TFP. Same sample taken to three different stores gets 3 different results.

 

[kimkats]

The last time I tested with the standard solution, I had to hold the tube in full sun for it to read 50. In shadow, it read 70.

This is why I say it. SO much depends on the conditions of where you are doing the test.