Testing CYA <30 ppm with Taylor K-2006 Kit by evaporation

[kodiak1120]

Hi everyone,

I'm a new pool owner (as of September of last year) and ever since last season, my CYA has registered zero on my Taylor K-2006 test kit (meaning I fill the test tube all the way up and still clearly see the black dot at the bottom), which is wierd becuase the prior owner of my house used triclor tablets in two floaters as their prior means of chlorination. Anyway, I've read that the Taylor K-2006 kit cannot measure CYA concentrations of less than 30 ppm, so I'm not sure exactly how much CYA I have in my pool. If I was closer to 30 ppm, I'd be fine just leaving it where it is, but if it is truly zero, I would obviously want to add stabilizer.

I was reading some other threads on here that talked about diluting water samples when the concentrations exceed the maximum testing limit of the particular kit, and that got me thinking that perhaps I could evaporate a certain percentage of a sample to test for CYA of less than 30 ppm, since CYA does not evaporate.

For example, if you had a 10 ml graduated cylinder, you could leave it out in the sun for a few hours and see how far down the water level was, and use that percentage as a basis for your test. So if you start out with 10 ml of water and end up with 5 ml, you could test that sample and then multiple your result by 0.5, etc. So if your test result showed 35 ppm of CYA, your actual CYA would be 17.5 ppm. If your sample went from 10 ml to 8 ml, you could take your result and multiply it by 0.8. So, again, if your test showed 35 ppm, your actual level would be 28, and so on.

Anyone ever tried this? I guess it may be a bit overkill, but I'd really like to know where my CYA level is since I used tryclor tablets at the end of last season.

Kevin

 

[JasonLion]

Re: Testing CYA <30 ppm with Taylor K-2006 Kit by evaporatio

The technique you propose will work. However, the required amount of evaporation takes a long time. You won't get enough to be useful in just one day.

Unless you have an indoor pool, the best thing to do is to add about 20 ppm of CYA. You might go a little over 30, but that isn't a problem.

You can get a view tube that allows you to measure levels down to 20. The TF100 includes that tube. Still, the CYA test is +-15, so measurements around 20 are not all that reliable.

There are some expensive electronic testers that work well at low CYA levels, but you don't see them around much because of the cost.

 

[kodiak1120]

Re: Testing CYA <30 ppm with Taylor K-2006 Kit by evaporatio

Thanks for the response... Will a longer tube work? I was thinking that the reagent just wouldnt' react with the CYA at concentrations less than 30 ppm. If it will, couldn't I get a very rough guess at how much CYA I have based upon how clear the liquid is? Meaning, if I pour the liquid in the test tube and it looks as clear as plain water, I would know that I am closer to zero CYA, whereas if the water is slightly cloudy, but the dot is still visible, I would know I am closer to 30 ppm?

Kevin

 

[JasonLion]

Re: Testing CYA <30 ppm with Taylor K-2006 Kit by evaporatio

Longer tubes work up to a point. The tube in the TF100, also available from Taylor separately, is longer which allows it to go to 20. However, as I said, the test is +-15 or so, which means the results are not as reliable at low levels as they are at higher levels. Likewise your comments about totally clear, vs a little cloudy are also true with the same limitation, the results are not perfectly repeatable so the level can still be 15 even if the water is totally clear. Also, it is very difficult to judge the amount of cloudiness by eye without some visual standard to compare against, and the scale is not at all linear, so a bit cloudy but dot not completely gone could be anything from 5 to 25 and picking a number in that range is rather speculative.