Yep exactly, when I'm about to test I'll empty out the RO water from the vial and put a small amount of test water in and give it a quick swirl and then empty it out. My thought is by doing that I'm getting rid of any sort of dilution from storing the glass vial with RO water to get a more precise result.My thought process exactly. RO water should suck up anything that might render a test inaccurate.