TF100 - Chlorine Test Question

[AndrewFH]

I'm completing the SLAM process on my swim spa and wanted to use a more precise measurement for the CC and OCLT at the end to confirm everything is a clean as possible. I am using a TF100 test kit and have read the extended test kit instructions. I understand that you can increase the precision by using a larger sample and using .2 for the drops as noted in this instruction.
"There isn't normally any reason to do this, but if you need more precision you can do this test with a 25 ml sample of pool water and multiply the number of drops by 0.2. In most situations the added precision is useless and simply wastes reagent."

I did have one question in doing this. After you get your FC level, when you add the R-0003 to start the check for your CC, do you still only add 5 drops? Or do you need to double that to 10 drops?

Thanks.

 

[jblizzle]

Good question that is not addressed in the instructions. You still only need 5 drops.

 

[AndrewFH]

Thanks.

 

[linen]

Why do you feel you need the precision? I personally don't see the need. If your OCLT is less than 1 ppm and if it takes only one drop to go clear when testing CC, you are good to go.

 

[AndrewFH]

@linen, I guess my reason is just my anal retentive side, and some lack of understanding of the chemistry involved. I figured more resolution, more precise results and I could be "more sure" the OCLT was less than 1 and no CC.
One question in regard to your comment "if it takes only one drop to go clear when testing CC". In my test kit (TF100), when you add DPD powder to the sample it turns pink. You then add drops of one reagent until the sample turns clear and count the drops. You then add five drops of another reagent. If the sample remains clear, there is no CC. If it turns pink again, you add the first reagent again until it turns clear again to get your CC level.
So I don't follow the "if it only takes one drop to go clear" comment? Perhaps you are using a different test kit that uses a different method?

 

[BoDarville]

So I don't follow the "if it only takes one drop to go clear" comment? Perhaps you are using a different test kit that uses a different method?

Since linen is currently offline and I'm currently viewing your post, I will take the liberty of fielding your question above (hope you don't mind, linen )

This applies to the TF-100 and the Taylor K-2006. The "one drop / two drops" statement refers to the number of drops of R-0871 that is added back to the sample (to get it to turn clear) after you have added the 5 drops of R-0003.

CC starts to be an issue around 0.3. That is the level where most common forms of CC start to cause minor irritation. Measuring at the 0.5 precision level (the standard test), it is assumed that any CC measurement of 0.5 actually means the CC level is quite close to zero, but just high enough to show up on the test. A CC of exactly 0.5 is incredibly uncommon. CC either tends to fluctuate around 0, occasionally just showing up on the test, or it tends to be 1.0 or higher. Sitting around 0.4 to 0.5 is quite rare.

The full guideline is that adding one drop of R-0871 on the CC test is fine but two drops is a problem, regardless of the precision you are using (0.2 or 0.5).

 

[AndrewFH]

Makes sense. Since I've started using the TF100 (which was just recently during a SLAM) my sample has not yet turned back to pink after adding the five drops of R-0003. I see what you are saying now.
Thanks.

 

[linen]

BoD has you covered, thanks BoD!

my sample has not yet turned back to pink after adding the five drops of R-0003.

Yep you have no measurable CC (regardless of using the 10 or 25 ml sample).