RO/DI unit install questions

[RCFA]

Originally Posted by Der_Iron_Chef

I rent as well, and I was concerned about not having to pierce the existing plumbing, which, obviously my landlord wouldn't have appreciated.

I installed my RO/DI unit in the same closet as my washer/dryer, and came up with the following install:


The little black hose is the RO/DI waste water, and it just empties into where the washer drains.

I am setting mine up just like this. The one thing that I am trying to decide on is the waste water hose. The manual says that you need to hook the waste line up so that there is back pressure on the waste water (by hooking it into a drain pipe before the trap)or it will not work properly. Any idea what this means or if it is necessary?