Windshield washer fluid in low temps?

I've lived in snow states all my life (except for a short jaunt in the Army) ... well ... even then, I lived in snow countries! But... I've never used anything but over the counter normal windshield washer fluid. I've never had it to freeze up, even in Indiana 20 degree below zero weather. If its mixed with any water at all ... yes it freezes. Had that happen many years ago when I ran water through my washer fluid resivour and pumped it through to the back window (mini-van). I then added regular washer fluid in the fall, but did not pump it out the back window. Well, the line froze. That was the only exception I ever had. I no longer have that car, and have never used water again for the windshield fluid.