Finding ultra-pure water locally...

I have heard automotive stores carry it, although I have not checked myself.

You can buy a jug of distilled water at any reasonably stocked drug store.

To my knowledge the purest water (h2o, nothing else) is from a reverse osmosis filter. Aquarium stores sell it as it is used to top off salt water / reef tanks as water evaporates, but adds no minerals, chemicals, or anything else that may hurt the tank. They call it RO water, and in my area I pay about 50 cents per gallon.

Regards, Alex

If I were you I would investigate a reverse osmosis system for your home from a local vendor that installs on demand RO systems for drinking water. You could have a tap installed straight off the unit so the water is not traveling through household plumbing. I know that lab grade RO systems provide water that is much, much, better than any water that can be produced by distillation. I assume the home units are pretty good too. Purified water, once its dechlorinated, can go septic pretty quickly, so you want a system that produces it as you need it.

HDM, any idea about difference between 9800-1 and 9800-5 grades of Reagent grade water?

I looked on the web and there are several companies that sell this.