I am not keeping this going to defend any manufacturer. Everyone is quite capable of making their own decisions. Trusting they research things. I merely posted because someone wanted ideas. Randy for instance is a chemist I gather and has way more knowledge and resources than I do to talk about that subject I certainly wont ever challenge his or other professional or established reefers unless I do have experience and knowledgeTrying to reduce waste water is not a win win. It has drawbacks of various sorts.
The entire RO/DI process is detailed here:
Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com