I understand what they do... but if your test using the OTO then do a further test using FAS/DPD shouldn't the values match?
I'm using the TF 100 (test in the blue box) to test pH and chlorine daily and then once a week I'm doing the full battery of test TA CH etc....
Should not the results from the FAS/DPD which gives me.... FC + CC = TC equal the total value I measured using the quick test? Or am I missing something.
I realize the OTO is a ball park measurement... but sometimes their not even close.
Also.. when doing any titration test (looking for a color change..) when is the test over.. when I get as much as a blush of the color Im looking for.. or a strong color change? ie if Im looking for pink... and the color turns to "pinkish" is that enough or should I keep adding drops until I get a "strong pink"