RO System FAQ

Generally, problems of a RO system can be divided into 3 categories: pressure, flow and salt rejection. The following lists of questions help to identify possible causes for these problems.


Why operating pressure is low?
Possible causes
  • Insufficient feed water pressure or flow
  • Pre-filter clogged
  • Solenoid valve not open
  • Pump rotating backwards
  • Insufficient power supply
Why operating pressure is high?
Possible causes
  • Concentrate or recycle valve plugged
  • Membrane fouled
  • -Membrane install backward
  • Feed water throttling valve closed or restricted flow
Why excessive pressure drop (high primary pressure, low final pressure)?
Possible causes
  • Restricted flow after pump discharge
  • Membrane severely fouled


Why permeate flow is low?
Possible causes
  • Low operating pressure
  • Membrane fouled
  • Operating on cold water
  • Flow meter inaccurate
  • RO system was shut down without flushing
  • Pre-filter clogged
Why concentrate flow is low?
Possible causes
  • Concentrate valve plugged
  • Concentrate pipeline restricted
  • Membrane damaged or rupture
Why water keeps flowing when machine is turned off?
Possible cause
  • Inlet solenoid valve not, closing or seating properly

Salt Rejection

Why permeate conductivity reading is high?
Possible causes
  • Membrane fouled
  • Membrane seal o-ring broken or damaged
  • Raw water quality changed
  • Membrane exposed to chlorine or other strong oxidant
  • Fouled probe or inaccurate conductivity monitor
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