Is shocking the only way to get rid of of combined chlorine, or can the normal addition of chlorine for general chemical balance eliminate small amounts of CC? In my pool, my CC is almost always 0 (i.e. not detectable using a Taylor FAS-DPD kit.) Every once in a while, however, I get a very low reading of around 0.2 ppm. After my normal dose of chlorine, my tests go back to showing 0 CC. Does this indicate that the small amount of CC was actually eliminated, or does it point to a small variation or error in the testing process?
I do know that during the FC test, the water can sometimes appear clear when it's still just barely pink. I'm careful to make sure that the water goes ALL the way to clear during the FC test, with NO residual pink, without adding any extra reagent.
On that note, does the addition of an extra drop of reagent during the FC test throw off the CC test? There are many times when the water seems REALLY close to clear, but not quite, so I add another drop. Usually I can see it clear up that last little bit, confirming the need for the last drop, but once in a while I feel like that last drop may not have been needed. It seems like this extra drop of reagent would cause the following CC test to be off by one drop because the first drop of the other reagent is "already there." Does the test work this way, or do the chemicals react in such a way that an extra drop during the FC test will not effect the subsequent CC test?