Deionized Water for Windshield Mix Solution

[jpnut]

All,
I had a question regarding washer fluid. I find that paying $2 to $4 every time I need to fill the windshield tank kind of annoying because the blue stuff can stain and seems like some brands just suck. Well I purchaed Rain-X concentrate mixer, and it can make many gallons of solution by adding an amount to ordinary water. So, I work in a place where I can use deionized water, should I use that "purer" water instead of tap? Thanks
-Jp