The 2 way watse water valve allows you to switch the waste water to either outside or to drain. You can run the reverse osmosis waste water outside to a storage tank or into a dripper system to water your plants.
The waste water doesn’t have to be WASTE water. By using the 2 way system it allows you to be able to divert the water between the house drainage which is normally when the waste water goes or out of the house to either a storage tank then to an irrigation system or have it direct plumbed to a dripper type system. Cutting down on unnecessary wastage water.