What to do with RODI waste???

[mark]

realize there more to being green than saving money, but at a dollar something for cubic meter (plus sewer cost as based on water in) my waste just goes down the drain.

Had thought about sending to the rain barrel for summer but since it's stays pretty full just with the rain, effectively I'd just be dumping the waste anyways.

Related question though, how for can you run the 1/4" OD waste water line without causing back pressure problems to the ro unit?