Low incoming water pressure is the most common cause. The system needs adequate pressure to force water through the membrane.
- Check your home's main water supply pressure. It must be within the operating range.
- Inspect the pre-filters (the first three housings). If they're clogged, they restrict pressure to the membrane. Replace them per the schedule.
- Verify the feed water valve is fully open.
If that didn't work: The RO membrane itself could be fouled or scaled, especially if you have hard water. It needs replacement every 2-3 years. Also check for a kinked or pinched 1/4" feed water line.
Heads up: Never connect the unit to a hot water line. Feed water temperature must stay between 40°F and 100°F (4°C and 37°C).