Conflicting TF-100 results

[frankinbahia]

I'm getting conflicting readings with my new TF-100 test kit.

ph = 7.2
TA = 80
CYA = 70
FC = 24
CC = 2

So far so good. The TC is what I expected, as I shocked two days ago to recover from algae. (And the TA sample turned to yellow instead of red, which I understand also indicates high chlorine.) The problem comes when I measure chlorine with the included Taylor K-1000 kit: 1 get a reading of only 1 (very light yellow). To double-check, I got out an older basic test kit I have, and with it I get what I would expect -- off the scale, very dark yellow/orange.

The water is blue and clear.

Anyone know why I get the apparently erroneous reading with the K-1000? (The kit is only about a month old.)

Thanks!

 

[spidey07]

The OTO and DPD tests react differently with high FC. One of them bleaches out quickly I can't remember which one. The only reliable test when shocking is FAS-DPD.

DPD bleaches out at high FC. OTO does not. Read the sticky at the top of this forum on extended test directions. It's a great read any way.

 

[duraleigh]

Anyone know why I get the apparently erroneous reading with the K-1000?

Make sure you are using the R-0600 reagent and not the R-0003

 

[frankinbahia]

SOMEHOW, the lookalike R-0003 bottle found its way into the K-1000 box.
Thanks, duraleigh!