I have almost never used the DPD test, but because of some problems this year I started to use it in order to get precise FC reading. My problem is that DPD and K-1000 kit give me very different numbers.
For instance: this morning when I tested with DPD it tells me I have 9 FC (18 drops) and .5 CC (1 drop). I then tested it with my K-1000 Kit and I get 4 FC.
Is DPD reliable only when shocking the pool (high numbers like 30 and more) or is it also precise in the low numbers like 2 to 5 FC? Why do I have a big difference like that? Which one is the good number?
Note: my DPD powder and liquid are at their third season (they should still be good I think), my K-1000 is brand new.