CYA Test Accuracy

[cschnurr]

I have always questioned my ability to measure CYA accurately, and have read the many posts here regarding test accuracy.
Especially useful was two-cya-kits-consistently-disagree-t37391.html?hilit=cya%20test%20error%20taylor%20cya

I have a Taylor 2005C kit and I have the CYA view tube that is supposed to make the test a bit easier.
I get quite repeatable results, but have I have never been convinced the results are accurate.

In trying to 'calibrate' my results I have used pool stores to compare my measurements.
Some pool stores match my measurements, but one pool store in particular always measures significantly lower CYA.
(All other tests are pretty close to my measurements)

In discussions with them they acknowledged they do not use Taylor test system (I'm pretty certain they use a Lamotte test system since my print out states 'WaterLink DataMate)
Unfortunately, this is the only store that I actually trust (Its a small independent Mom & Pop shop that have never tried to sell me anything that I didn't already know I needed)

Last year, as an experiment with the store, I purchased a small vial of Taylor R-0013 from them and asked them to test my water using both systems. They confirmed my result using Taylor, which if I recall was 30ppm higher than their test test results. They could not explain the difference except to say that they are not as experienced with the Taylor method to accurately determine when the dot becomes obscured, and that their experience in real life confirmed their results.

I have a SWG that requires CYA to be 60-80. This year, my Taylor kit consistently measures 40, while the store testing measured 80. It is not in the stores best interest to measure low as I think I need to by CYA from them and they are saying I don't need it. (they didn't try to sell me anything else)

Additionally, I have found that my best year for pool maintenance/algae was before I purchased my test kit, and relied solely on this stores CYA test results.

Is there a fundamental reason why Taylor and Lamotte tests results differ? or is there some other factor why the results would vary?

 

[Bama Rambler]

Pool stores are notoriously wrong on cya tests. I've had them show cya in tap water on several occasions. I'd trust your own results.

 

[woodyp]

I gotta try that just for grins Bama! They're usually double what I measure.

 

[JasonLion]

The better CYA tests are +-10 under ideal conditions, and much more commonly +-20. Most of electronic testers, including both of the ones commonly used by pool stores, are significantly less precise than that. Plus there is plenty of room for operator error on the CYA test.

The only way to really know what is going on is to purchase some calibrated CYA reference solution (Taylor R-7065) and test that with the different tests.

 

[carlscan26]

Jason just beat me to it, but here's a link to where you can buy the R-7065: http://tftestkits.net/R-7065-CYA-Standard-Solution-p34.html

I had the same concerns as you; so I bought this standard as well as a large bottle of CYA refill (http://tftestkits.net/R-0013-CYA-Refill-8-0z-p52.html) so that I can run the test as many times as I want without running out of reagent.

I always run the standard solution first to calibrate myself for the conditions (amount of sunlight, etc.) I used to read the standard at 60-70 until I played around with how high to hold it, where I stood in my yard (I have two different colors of concrete), how bright the sun was that day. Consistency is key! I got pretty good at it actually in the summer. However, come winter and cloudy skies and my ideal conditions were no more, so I found myself recalibrating to a new position, etc. Same thing for time of day - I couldn't always measure at 10am, and the sun's location changes throughout the year. Is this overkill/ridiculously anal retentive of me? Yes, but this is what I've done to feel confident in my testing.

Just my $.02 but with CYA being so key to the TFP/BBB method I think it is well worth it to get the standard solution.

 

[woodyp]

You guys been holding out on me! (or most likely I just missed it) First time I've ever seen anything about a "standard solution" mentioned. Anything to help me get a more accurate reading would be a blessing. Off to order some now. THANKS!

 

[carlscan26]

 

[cschnurr]

Thanks to all for the great response.
I guess I need to buy some standard solution.

Two questions.

1) Does the CYA standard have an expiration date? I'll likely only test CYA every couple weeks ( 8-10 times/ season)
I'm not quite sure if carlscan26 is suggesting that I mix the CYA 50ppm standard with R0013 and keep in it a separate bottle so I can use it over and over throughout the course of the year? or just recommending I order the large bottles to make sure I'll never run out.

2) Does TFTestkits ship to Ontario, Canada?

 

[duraleigh]

The standard solution is available for CH (200ppm), CYA (50ppm), and TA (100ppm). They have no expiration dates.

However, Taylor Technologies does not allow any of it's customers to ship any Taylor product into Canada from the US.

 

[jkapp]

Although it wouldn't be as accurate as R-7065, for those outside of the U.S., is there a way to create a reasonably accurate reference solution using tap water and CYA powder?

 

[JasonLion]

There is no easy way to produce a sufficiently accurate test solution without laboratory grade equipment and laboratory grade chemical supplies.

The Taylor calibration reagent is available world wide, however prices are sometimes far higher and you may have to search fairly hard for people who import it to your country.

 

[mwkelly]

I know I am new to TroubleFreePools but I do have some experience in running tests that use the "black dot" method. The key is to control the light shining through the vial as well as the ambient light.

I plan to use the light from my speedstir and conduct the test in a room where I have total control over the ambient lighting. This should enable me to have consistent results. Now that doesn't guarantee the results themselves will be accurate but they should at least be consistent.

 

[JasonLion]

The CYA test needs very bright light. I doubt that your average indoor light or the speedstir will be nearly bright enough. Some pool stores use a small daylight simulator, but they can be expensive.

 

[CaOCl2]

See last post in this thread:
cya-testing-t34850.html

 

[CaOCl2]

cschnurr, I'm sending you some Standard Solution.

 

[cschnurr]

Thank you Paul (CaOCl2), your the best.
I'll post my results along with the PS testing of the solution once the weather starts to look like swimming is on the horizon.

For anyone looking for Taylor reagents in Canada, Apollo Pools in Montreal has a website at
http://piscines-apollo.com/cubecart/index.php, they have always been prompt, and reliable.

 

[lefty51]

The better CYA tests are +-10 under ideal conditions, and much more commonly +-20. Most of electronic testers, including both of the ones commonly used by pool stores, are significantly less precise than that. Plus there is plenty of room for operator error on the CYA test.

The only way to really know what is going on is to purchase some calibrated CYA reference solution (Taylor R-7065) and test that with the different tests.

Hi Jason, I hate to bring up an old thread. But with this lack of sunshine this month and being new to the TF100 CYA test, I'm trying to figure out a lighting setup where I can test CYA on days like today. I know, more POP !

I'm waiting for FC to drop back down to test PH and I'm bored

Anyway the question is, if I get the reference solution and use it to compare with my solution is it possible to setup a lighting situation that would be accurate and repeatable.... providing my bulb did not burn out and replaced it with a different wattage ?