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

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