This is now solved. It is safe. I wrote several people and here is one response.
DE-Ionization is not a property or condition. It's one of several types of processes by which water can be purified. The amount of purity is usually stated in RESISTIVITY, like 10 megaohm (see attached table). Water is usually considered to be "deionized" when its resistivity is greater than 1 Megaohm yet there is no stanard or definition of what quality is deionized.
Deionization is accomplished by passing water across ion-exchange resins that have "chemically active sites" on them. Cation Resins have chemicall active sites that contain a Hydronium ion (H+) on them. Anion resins have sites that have a hydroxyl (OH-) on them. As cations pass by the cation resin, atoms like Sodium (Na+) are exchanged for the Hydronium and as anions like Chloride (Cl-) are passed over the anion resin they are exchanged for the OH-.
Since all of the Sodiums and Chliride are now gone and exchanged for the H+ and OH- (which combine to make H2O) the water is now free from cations and anions and is deionized.
Note that all cations and anions are removed in this way, not just the Sodium and Chloride. Even dissolved gasses can be removed because almost all dissolved gasses are polar.
De-water cannot harm the body because you stomach is 1 molar hydrochloric acid. This is close to 3%. The ions will simply be more dilute. Because DI water removes dissolved gasses, it is very bland.
The best waters are usually produced by reverse osmosis because they can remove up to 99% of the dissolved solids but rarely removed dissolved gasses leaving the water with good taste.
David K. Silverman
Chemical Engineer
Certified Environmental Specialist
Certified Environmental Inspector
I am still waiting on a response from the EPA, but I suspect it will be similar.