How long has it been since you used your RO
Typical membrane life is 3-5 years with proper care.
I got my unit 3 years ago from airwaterice.com. My unit has a flush valve that lets me flush the membrane after I'm done, and before I start a RODI
session. I only use my system every 3 weeks or so to make a new batch of top-off water, and water for a water change.
"Membranes need to be replaced when any of the following are true.
You notice Poor taste or water quality. You may have changed all of the other
filters and the water still tastes bad. Your membrane has degraded with age and
is not performing as well as it should. Typical membrane life is (3-5) years,
Excessive poor tasting water, the membrane has been compromised and water
is flowing freely through it. Most common cause is CHLORINE exposure. Poor
filter maintenance or poor quality carbon filters are usually to blame. Or, when
not much water is available, the system seems to have lost its pressure. The
membrane has become fouled and is not making enough water."