This appears to be a very simple concept to save wasted water from your RO unit. I recall looking at this before but only recently did I become interested as a result from another thread.
So they do sell retrofit kits but I figure one could easily find parts locally and make this a simple DIY project and perhaps even improve on it. So lets discuss.
Links:
https://www.wattspremier.com/product...e-Retrofit-Kit
https://www.freshwatersystems.com/p-...id=10050&qid=0
http://www.costco.com/Browse/Product...=1&topnav=&s=1