My intake water is 140PPM. My waste water is 158PPM. If you cut off the flow for the waste water like described above, the RO unit is doing no good. If you reuse the wastewater to flow through again, the RO unit is first trying to separate 140PPM, then 158PPM from the first batch of waste water, then from another cycle this amount will continue to increase and the RO filter will be destroyed very quickly. This incurs much higher cost to replace the RO filter, which is more expensive than all five other filters on my system combined.
The RO filter wastes this water for a reason. I did not mean you cannot use it to water plants, wash clothes, whatever. I meant you should not close off the waste water line, you should not use for drinking water(unless you are happy with water that has more impurities than tap), you should not re-run RO waste back to the RO...
The way to combat waste water is to remove the RO filter from the setup completely, run it through more carbon and sediment filters, and then run it through a few DI filters(I would recommend at least three). This will, however, cause you to need to refill, replace, or renew your DI filtes much more often and is not really recommended as a perfect solution yet.