I suspect the DW spec started just to reduce wear on the metals in the atty from impurities.
If you have
good tap water at home, that should be fine considering the minute amounts we're talking about.
At the store... "drinking" water should be just as good. They're heavily filtered.
I'd avoid any "mineral" waters, as they're specifically produced to retain, or have added, extra minerals and salts for flavor.
Can't say about "spring" varieties... some might, some might not. I'd avoid for constant atty use.
For generic or common brands... all three cost the same per gallon, so get DW if available, drinking if not
But I wouldn't get neurotic about the topic.
