@slaw
It depends. First on the quality of distilled water (which is standard), and the sample of RO water (which is not).
If I were doing that measurement, I would try an instrument called a 'megger', which typically reads resistance with the help of a high voltage supply. Since I don't need one, I don't have one, and just bite the bullet and buy pharmacy distilled at $1.50 a gallon. Lazy? Yeah - but that's just me.
It depends. First on the quality of distilled water (which is standard), and the sample of RO water (which is not).
If I were doing that measurement, I would try an instrument called a 'megger', which typically reads resistance with the help of a high voltage supply. Since I don't need one, I don't have one, and just bite the bullet and buy pharmacy distilled at $1.50 a gallon. Lazy? Yeah - but that's just me.