Does water return to pink after time when testing FC?

[capricatunes]

After I add the R-0871, and the water becomes clear, I have noticed that - if the water is left in the vile - after a minute or two the water will once again return to pink. Is that normal? Or does that mean that I am doing something wrong?

I’m using the TFP test kit and the Taylor speedstir.

I found this, so I think I’m good?

Water Testing Errors - Further Reading

www.troublefreepool.com

“...the pink color slowly comes back over time even when you add nothing. This is why Taylor explicitly says that the ENTIRE test (FC and CC) needs to be completed in under 1 minute from the time you add the powder to the water to the time you finish counting the last drop for the CC test. Even taking time to write down numbers between tests could cause errors.”

 

[mknauss]

That is normal. Once you have completed the FC test, immediately move on to the CC test, if desired, or dispose of the sample.

 

[BenB]

My guess on the reason was because the sample is now exposed to 360° sunlight, UV, and greater temperatures which burn off the chlorine in the sample very quickly, leaving nothing for the reagent to react with and make it clear again.

Is that how the chemistry works?

 

[mknauss]

The chemical reaction between the reagents and chlorine. I am not familiar with the exact chemistry.

 

[Dirk]

Three stars!
You're testing is good.
You found the article to confirm that.
And you double-checked on the forum, which will likely answer that question for someone else!
All good!!