Don't just get out the biology book. Read it. Osmosis is transport of the water across the membrane. The salts and organics don't move across it, which is why it works. Before plunging into RO, though, explore whether you need to get rid of the natural organic ingredients in the water supply, and whether carbon filters will do it for you. Jol Sprowles, Ph.D. Senior Process Engineer Tyco / Electronics / Printed Circuit Group - Stafford Division Phone: (860)684-5881 ext. 263 m: Chuck Brummer <[log in to unmask] <mailto:[log in to unmask]> > Subject: Re: Water Wash system justification X-To: Kathy Kuhlow <[log in to unmask] <mailto:[log in to unmask]> > MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Wow, Get out a biology book. Osmosis is the transport of salts and other ions across a membrane. Ions, especially salts, will always move from the higher concentration to the lower concentration. I think the guys are correct in suggesting there is an ulterior motive for suggesting softened instead of DI.