Description-Flow Restrictor RO System
Benefits -Flow restrictors
- Flow Restrictor RO systems restrict the flow of concentrate( waste) to optimise water economy.
- Ensures adequate back pressure for optimum pressure of membrane.
- Ensures RO membrane pores don’t get prematurely fouled by dissolved minerals.
- Different capacities available from 200 to 1500 cc (ml)
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.
Example Calculation: You have a 80 gpd membrane, have relatively poor water conditions including hard water(like in Perth or Brisbane) and want to maintain a minimum waste :pure water ratio of 4: 1.
80 GPD = 80/24 GPH =3.3 GPH = 0.056 GPM.
0.056 GPM =021 Litres/min or 210 ml/min .
Hence flow restrictor should be sized 210 x 4 ml/min equating to approximately 800 ml/min.