Just found out a couple of weeks ago that the company where I work makes DI water in HUGE quantities. I knew we did our own water treatment, but I thought it was just to prep wastewater for discharge, EPA stuff. Normal levels are maintained at approx. 2200 gal. The generator kicks on when the level goes below 1800 gal. They'll purge a few dozen gallons on a whim just to wash out some of the equipment parts. I got the go ahead to grab a gallon or two whenever I need some. Just got to be careful not to open the 2" purge valve too far or I'll get washed away.