there are now high efficiency RO/DI units that will make the ratio any where from 1/1 or 2/1 in favor of good water, but they are pricey
http://www.spectrapure.com/low_waste_systems.htm
I bought a refurbished 90 gpd unit that looked new for $128 that I also needed to buy a booster pump for since my water pressure is only 35psi, the happy range for a RO unit is 65 psi. Here is a link to the unit I have
http://www.spectrapure.com/St_RODI-REFURB.htm
I have the unit in my laundry room hooked up to the cold water pipe going to the washing machine and the waste water going into the washing machine drain pipe