I'm pretty finicky about doing my water tests; I use exactly the number of drops called for, hold the bottle vertically instead of at an angle and generally follow the instructions to a "T". I occasionally take a water sample to my local Leslie's just to see how well their results agree with mine. Of the three employees that work there on different days all three have a different way of doing the tests. The worst one typically overfills the sample vials, puts in 8 or 9 drops of reagent when it calls for five, shakes the sample to mix instead of inverting, etc. Just wondering how sensitive these tests are to following the instructions exactly vs. just getting it sorta close. What's your experience?