Gardening and Horticulture - Drip Irrigation System (project)

I have a drip irrigation problem I need help with. It will help if you understand what the whole scenario is.

I have a reverse-osmosis water filter and, for those who don't know, this type of water filter system rejects about 3 times as much water as it processes (just part of the system I guess). So what I am trying to do is use this water for a drip irrigation system. What I have so far is a 1/4" tube (the same kind used for an ice maker) connected to the exit for the rejected water from the filter.

I can get the water supply to a couple of plants I want to water but the unit puts out too much water for the two plants. So I need to restrict the water flow to the plants but the rejected water out of the filtration system still needs to drain somewhere so I can't restrict the flow of the rejected water from the system, if I do that the system won't filter any more water until it can get rid of the rejected water.

So that is the deal and I don't know how to get past it. Anyone?

Why not direct the surplus elsewhere, such as a drain?

Rejected water that exits the filtration system would go to the path of least resistance. At the end where the plants are the line is capped to create back pressure so I can control how much water goes to the plants. With this back pressure that means the path of least resistance would be the one that goes freely into the drain. Which means it would exit the tube at the drain before it gets to the plants. If I put the drain at the very end of the whole system then I would need to still create the back pressure for controlling the water to the plants. I can't restrict the flow of rejected water out of the filtration system like that, no filtered water would get processed.

Thanks