Don't want to hijack your thread, but I have a 3 tank DI set up from a company called Hydrologix here in VA. It has a carbon bed and 2 mixed beds, no waste water and takes all of my tests to "0" This company is actually a commercial water treatment equipment operation that does a lot of hospitals, dialysis units, etc. They also do pet stores now. Some of the hobbyists got them to start doing these set ups for us. No installation charge, no equipment charge and it costs me 17 cents per gallon (based on your city water quality). I can make 5 gallons of water in about 15 seconds with no waste.
Point is, you guys should see if there are companies in your area willing to do something similar. With such large tanks, I can't imagine the time and waste water you go through to get what you need.