Just to clarify for anyone else out there (the train of thought up above might be confusing to some):
If your waste water goes into the washer, if you don't turn the RO/DI off or have it set up to shut itself off with a solenoid...your washer will overflow.
If you fill your washer up only halfway with waste water and want to run a load of laundry, the washer will fill itself up to the level selected on the washer. So, if you want to run a full load of laundry and only have the washer half full of waste water, the washer will know to add another half bin of water.