Flow Restrictors create back pressure throughout the reverse osmosis membrane element and maintain a desired ratio of reject flow (to drain) and permeate (product) flow.

Availability: In stock (can be backordered) SKU: RO009 Category:
  • Description
  • Size Guide
  • Additional information
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Sizing Flow Restrictors:

Every reverse osmosis unit has a device called a flow restrictor that determines the amount of water that flows to drain. In general, the flow restrictor must be sized to fit the membrane production size. The flow to drain is usually about four times the membrane production rating, although the drain flow ratio often decreases a bit as membranes get larger. The flow restrictor also provides back pressure within the membrane in order to maintain a specific permeate/waste flow.

Part of the difficulty in understanding this ratio is that membrane production is usually given in gallons per day (gpd), while flow restrictors are usually sized in milliliters per minute (mlm). To convert, multiply mlm by .38 and the result, roughly, will be gallons per day.


General Guideline for Flow restrictor sizing.

RO Membrane Size
(Gallons Per Day)
Use Flow Restrictor
(ML Per Minute)
8-20 GPD150
21-25 GPD250
36 GPD350
50 GPD500
75 GPD750
100 GPD1000
150 GPD1200
flow restrictor08022





Additional information

Weight0.1 kg
Dimensions6 × 6 × 5 cm


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