DI water is not hard to come by. You can buy filter kits at your local membership big box stores. We have a DI system at home. Just flip the lever and out it comes.

 

My mistake. We have an RO system at home, not DI. Reverse Osmosis.

 

I have seen deionized water at the supermarket or other general stores. It is not a big deal. That or distilled is perfect.

Here is an internet definition:

Deionized water (DI water, DIW or de-ionized water), often confused with demineralized water / DM water,[3] is water that has had almost all of its mineral ions removed, such as cations like sodium, calcium, iron, and copper, and anions such as chloride and sulfate. Deionization is a chemical process that uses specially manufactured ion-exchange resins, which exchange hydrogen and hydroxide ions for dissolved minerals, and then recombine to form water. Because most non-particulate water impurities are dissolved salts, deionization produces a high purity water that is generally similar to distilled water, and this process is quick and without scale buildup. However, deionization does not significantly remove uncharged organic molecules, viruses or bacteria, except by incidental trapping in the resin. Specially made strong base anion resins can remove Gram-negative bacteria. Deionization can be done continuously and inexpensively using electrodeionization.

Three types of deionization exist: co-current, counter-current, and mixed bed.

 

Good for you
I live on a small Island, finding anything better than 92 Oct. Is a pipe dream round here. I'm thoroughly done with this thread though so as long as the Google expert classes are through have a good day

 

Ro systems basically lowers the conductivity of exit water and remove heavy salts in my opinion vg for radiator addition
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