Ok did not know. I saw they were talking about water softeners what I know about them alot of them use salt to soften which I donnot think it would be good for machines. I know about residnetal water softerns I might be wrong about the other softeners out there.
Tony...Here these guys would be able to answer the DI through the machine questions: http://www.finishing.com/147/97.shtml
One guy says add a little sodium carbonate (aka filler...lol)