Different FC results using different test kits

[yardoasis]

I've been using the TF100 kit once a week to get a full set of results, and using my basic color matching test kit from Leslie's during the week just to see the FC and pH in the evenings.

But today was the first time I tested FC using both kits, out of curiosity. The color matching test showed a FC level of about 4. But when I tested using the TF100 kit, I got a FC level of 9.5! I tested both within a few minutes of each other, while the pump was running.

Has anyone gotten vastly different FC results using different test kits? And does the color matching test tend to give lower numbers?

 

[Richard320]

If it was the pink colormatching test, you might have started bleaching out the reagent with high FC.

If it was the yellow... hard to say. I used to do both tests every time to try to calibrate my eyes. Anything from 4 to 7 all looked exactly the same to me on the OTO test.

 

[yardoasis]

Yeah, it was the pink color matching one. Guess I should really start using the OTO test.

 

[JasonLion]

The FAS-DPD test is always the most reliable. The others have an assortment of things that can affect the results.

 

[connie249]

I have the same problem. Except that I am using the yellow test that is included in the TF-100 kit. The yellow test result is almost consistently half of the pink result. I have found if I allow the yellow test to sit for a few minutes the color gets darker. Yesterday it increased the count increased by 1.5ppm after just a couple minutes sitting on the counter.