We installed a Deionized water system in our coach. I can use it to wash the coach, as it has a 1,500PSI pressure washer. We also use it to fill our fresh tank with Deionized water. We do have a bypass, and typically add a little city water to the tank (about 5%) as pure DI water is aggressive, and will dissolve metals form our water system (brass in our manifold, etc) also pure water will not conduct electricity, and our fresh gauge will not read unless there are a few impurities. As Jack said it is not cheap. It cost us about $80 to change the resin beads, and I typically can generate about 1,000 gallons per charge. The big plus is our water heaters, drains, shower all look like new with 0 deposits.
Steve & Rhonda Bennett
Dana Point, CA
92 Marathon XL40
2012 Jeep Rubicon Unlimited
Owner: California Coach Company, LLC