Silver Supporter
Apr 21, 2020
Apex, NC
As you can see in my signature, I use the K-2006 kit. For testing FC and CC, I use the FAS-DPD test. I have a question about the CC test. It says after adding 5 drops of R-0003, if the sample turns pink, add R-0871 until it turns clear again. Every time I run this test, the sample turns the very slightest of pink. You can barely see the pink. One drop of R-0871 easily turns it clear. It seems to me that the CC is closer to 0 than to 0.5ppm. Should I be recording this as 0.5ppm as I have in the past? I have not been running the 25ml test but it wouldn't surprise me if I got a 0.2ppm result.

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
Texas, San Antonio/Marion, South-Central Area
Pool Size
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
Should I be recording this as 0.5ppm as I have in the past?
If there is slight pink and it only took one drop, then officially you can call it 0.5. But overall anything that low we don't worry about it and consider it zero. All good. :goodjob:


TFP Expert
Platinum Supporter
May 23, 2015
Tucson, AZ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
My opinion os that your CCs are zero. One drop of titrant is the limit of the test so it’s statistically insignificant if it’s one drop. That faint color you see can easily be coming from air oxidizing the DPD dye as it is sensitive to oxygen.

The answer is effectively 0. If you did the 25mL test, my bet is it would be one drop also. Again, that’s effectively 0.
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