Is Reverse Osmosis Water Flowing Slowly? Here Are the 5 Most Common Reasons
If you notice that water from your reverse osmosis system is flowing slowly, and you can’t call a technician or prefer to diagnose the issue yourself — this guide will help you.
1. Low Incoming Water Pressure
Typically, water pressure in the plumbing network ranges between 3 and 6 bar (atm). This is sufficient for the water to pass through the RO membrane. If pressure exceeds 6 bar, a pressure reducer is recommended to protect both the filter and other home appliances. If the pressure is too high, the four-way valve may stop functioning. If the pressure is below 3 bar, your system should include a booster pump.
Pressure drops can also be temporary — due to treatment station malfunctions or pipeline issues. In multi-story buildings, water pressure may fluctuate, especially on higher floors during peak water use.
2. Bent Tubing
Check if any of the hoses are kinked or bent — this can severely limit water flow. Also make sure that the inlet valve and the tank valve are fully open. While rare, this is a simple issue worth ruling out.
3. Clogged Pre-Filters
Dirty pre-filters are the most common reason for low system performance. Clogged cartridges or an exhausted membrane slow down tank refill times. Possible causes include:
- Filters not replaced on time (max lifespan is ~6 months)
- Heavily contaminated water (e.g. rusty)
- System unused for a long time (e.g. 1 month), allowing bacteria or biofilm to develop in sediment and carbon filters
Solution: Replace pre-filters.
4. Damaged Storage Tank
From our experience, high water pressure can cause air to leak through the tank valve. If the internal bladder is damaged, the tank must be replaced.
You may try re-pressurizing the tank using a bicycle pump — the air pressure should be around 0.3–0.5 bar. Use a precise digital pressure gauge.
5. Worn-Out RO Membrane
This is less common but still possible. If you’ve checked everything else and the problem persists, the membrane might need replacing.
General Tips
The most frequent reason for low RO water flow is a pressure drop — and pressure is key for membrane efficiency. When you notice reduced flow:
- Check if water flows from other taps
- Inspect tubing and valves
- If you have a pump (electric or manual), make sure it’s working
- Check if the tank is full or empty
- Recall when the filters and membrane were last replaced
If the issue remains — give us a call and provide these details. It will help our technician diagnose the problem faster.
Understanding how your RO system works makes troubleshooting easier. And if you’re not yet using reverse osmosis — now’s the time. Choose quality and daily comfort!
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