The lab I got the DI water from said it's 18.3 ohms. I never heard of ohms when speaking about water
That'a an incomplete specification, and unless you have some really salty water, it's incorrect as well. The correct term is "specific resistance" and it's the resistance measured by two plates with an area of 1 square centimeter each, 1 centimeter apart, dunked in the water. Pure water measures about 18.2 megohms or as conductivity, its reciprocal, 0.55 microsSiemens. So assuming that "ohms" is water processor slang for megohms x cm, you got a pretty good jug of water.
Of course this is only a measure of the ionic content. You can't measure carbon dioxide absorbed from the atmosphere or organic contamination by measuring electrical resistance.