Total Alkalinity question

[Zyriak]

I just have a quick question that's been bothering me a couple of days now.

Have i understood it right that the TOTAL alkalinity should be somewhere between 80 - 120 ?

I read the manual for the AquaCheck 15 sec. test-strips.. and there it says...

For best resaults on stabbilizer ( Cyanuric Acid) test, pH should be between 7.0-8-4 and Total alkalinity should be at or below 240.. does this mean that the stabilizer test will get wrong if the total alkalinity is over this level?

checked the levels last night.
( I am Shocking the pool at the moment ).

pH: 7.0
Chlorine:10+
ppm TOT ALK: around 60
ppm Stabilizer: around 60

[chem geek]

I don't know why they say that. At any rate, your TA level is fine for what they say and you don't want it very high unless you are using Trichlor as your chlorine source. Just keep in mind that test strips are not nearly as accurate as a good drop-based test kit such as the Taylor K-2006.

[Q]

Water temperature is a source of error when testing cyanuric acid in pools. This primarily occurs with the turbidimetric tests. A 20° F increase in temperature from normal testing temperature can result in a 10-20% decrease in the CYA readings. A 20° F drop in temperature can result in a 10-20% increase in the CYA reading. So if a water test sample reads 50 ppm CYA at 75° F, this same sample could read 60 ppm at 55° F. Conversely, this water sample could read 40 ppm at 95° F. It is a see-saw effect, as one goes up the other goes down. Table 1 gives an example of test results for both photometric and visual determinations of CYA as a function of temperature.

Test strips use a colorimetric reaction that is compared with a color chart to determine the concentration of CYA. It is important to understand the chemistry of the colorimetric reaction to understand some of the limitations of test strips in determining CYA.

Most test strips use a combination of melamine and a pH indicator to determine cyanuric acid concentration. Melamine reacts with CYA in the controlled environment of a test strip pad and results in a small change in the pH. This change in pH is exploited with the use of a pH indicator to produce a colorimetric test for CYA.

Because the test strip method measures a small pH change, it is important that the pH of the pool being tested is close to the ideal pH range. If the pH of the pool is not in the ideal range the accuracy of the CYA determination can be reduced.

High alkalinity can also have an impact on this test. So, it is best to adjust the pH and the alkalinity level in the pool before testing with CYA test strips.
http://www.apsp.org/utility/showArticle/?objectID=1091

[chem geek]

Good turbidimetric CYA tests such as found in the Taylor K-2006 are not affected by temperature in the way the APSP describes. This is because the test changes the pH to force precipitation of melamine cyanurate. If that was not done, you wouldn't even be able to measure 20 ppm CYA since that is roughly its solubility near room temperature.

For test strips, what you wrote sounds very reasonable, but is yet another reason not to use test strips and explains one reason why the CYA test is very unreliable when using test strips. Thanks for that info on the CYA test in test strips -- that was very useful.

[Q]

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

With one exception, no. Our lab has run the pH, total alkalinity, calcium hardness, free chlorine, and cyanuric acid tests on known standard solutions at approximately 104°F, 75°F, 60°F, and 40°F.

Only at 40°F did the CYA standard solution test higher than its actual value (after accounting for test variability). All other tests were unaffected by temperature differences.

http://www.taylortechnologies.com/Chemi ... ntentID=86

[chem geek]

Thanks for that reference. That's good to know if one is testing CYA levels of very cold water. Note that 40ºF is getting close to freezing while 60ºF is still cold water and didn't show any issues. This is why I wrote that, for practical purposes, the test is not temperature-dependent, at least for the Taylor turbidimetric test. Again, what you wrote in your earlier post of the CYA temperature dependence and other problems with the CYA test regarding TA are for test strips and helps explain why test strips really aren't very good for testing CYA (and they aren't great for some other tests either -- they don't test for CH, for example, and only for Total Hardness).

[Dproctor]

My Alk and PH are low, and I have no chlorine showing up on strips or test kit. I have added stabilizer and that didn't help... pool place said I have mustard algae and I've been treating for that, but today I added 5 lb of alk increase and 2 bags of shock and some algaecide... when I shock water turns green.... not sure what the heck is up with my pool... but I'm sick of sinking money into it! Help!