Drain Water Flow Controls for RO System Dispensers:

Flow Restrictors (Flow Controls) are Required for All Reverse Osmosis Systems. The Flow Restrictor Must be Properly Sized to RO Membrane Capacity.Flow Restrictors Create Pressure Throughout the Reverse Osmosis Membrane Element and Maintain a Desired Ratio of Reject Flow (to Drain) and Permeate Flow. 

It is Recommended that You Replace the Flow Restrictor Each Time You Replace Reverse Osmosis Membrane to Keep System Operating at Peak Efficiency. The Flow Restrictor Should Match the RO Membrane's Production Rate.