Flow Restrictor Purpose Flow Restrictors (also known as Flow Controls or Capillaries) are required for all reverse osmosis systems. The Flow Restrictor must be properly sized to the 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 (product) flow.
It is recommended that you replace the Flow Restrictor each time you replace your reverse osmosis membrane to keep your system operating at peak efficiency. The number on the flow restrictor indicates the flow rate, in milliliters per minute. The flow restrictor should match your reverse osmosis membrane’s production rate.