CYA test for lower values...

[UnderWaterVanya]

We have recommended dilution when trying to discover the extent of very high CYA levels. Is the opposite possible as well? If a pool has less CYA than can reliably be measured can you change the ratio of reagent to water lets say 3.5 ml water to 10.5 ml reagent to measure low CYA? My assumption is that if this worked the result would read twice as high as the real CYA level, which would mean that a 15 ppm CYA would test as 30ppm - our am I misunderstanding, is it the opposite ratio that is needed?

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[duraleigh]

Any time you dilute ANY of the tests for pool water, you dilute your accuracy as well. The whole point of the testing we suggest (over strips) is better accuracy to begin with. I am not a fan of dilution for ANY of the tests although there are some occasions when it may be MODESTLY helpful.

The CYA test is practically accurate to within plus or minus 10ppm at the correct 50/50 ration. Trying to measure less than 20ppm is hardly worth it at full strength and impossible with any form of dilution.

PS - some of you might think I am interested in selling more reagents. Nope. However, I am very interested in folks keeping the tests we suggest as accurate as is practical. Anything else goes against all the things we teach.

 

[UnderWaterVanya]

In this case I'm saying you would be doing the reverse of dilution. In fact accuracy might go up just like when you go to a larger sample in the FC test. However I haven't tried it since my pool's CYA is over 50 and I could not easily get a read on the accuracy.

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[duraleigh]

Oops! I should've read your post more carefully....sorry!

I still don't think it will work but let me think on it a bit.

 

[JasonLion]

It is possible, but quite tedious to do what you want. You have to leave the water sample out until exactly half of the water has evaporated out of the sample. Then divide the test result by two to get the actual value. The precision will still go down, not up. Though the loss of precision won't be as large as it is for regular dilution.

 

[UnderWaterVanya]

It is possible, but quite tedious to do what you want. You have to leave the water sample out until exactly half of the water has evaporated out of the sample. Then divide the test result by two to get the actual value. The precision will still go down, not up. Though the loss of precision won't be as large as it is for regular dilution.

That is tedious.

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[CaOCl2]

You can mix 3.5 mL water sample with 3.5 mL of CYA Standard Solution then proceed with the test (ie add your 7 mL R-0013). If you read 30 ppm on the view tube then there's actually 10 ppm in the pool water. What you're basically doing with this method is diluting a known standard.