Common Issues with Osmosis Drinking Water Systems and How to Fix Them

Every plant manager, production director, and technical decision-maker in bottled water factories, beverage plants, pharmaceutical facilities, and municipal waterworks has faced unexpected drops in permeate quality or sudden production stops. These problems always appear at the worst possible moment. After servicing more than 800 industrial reverse osmosis drinking water systems across Asia, South America, and Africa, Guangdong Morui has identified the seven most common failures that account for 95% of all emergency service calls. This guide shows exactly what goes wrong, why it happens, and the precise steps our engineers take to restore 99% salt rejection and full design capacity—usually within 24-48 hours. The MR-BWRO-10TH and larger custom plants we install all share the same vulnerability points. When operators understand these failure modes and apply the correct corrective actions, system uptime exceeds 98%, and membrane replacement intervals stretch to 6-7 years even with challenging feed water.

Most Frequent Performance Killers and Permanent Solutions

These issues appear in every region we serve, from high-silica groundwater in Southeast Asia to iron-rich well water in Latin America.

Membrane Scaling – Calcium Carbonate and Silica

Scaling remains the number one cause of flux decline in brackish water plants. LSI values above +1.8 or silica exceeding 120 ppm in the concentrate stream trigger immediate precipitation. Operators first notice rising differential pressure and falling permeate flow while rejection stays acceptable.

Fix: Inject certified antiscalant at 3-5 mg/L before the high-pressure pump and maintain recovery at or below 70% on the MR-BWRO-10TH series. Perform acid cleaning with citric acid at pH 2.5 when normalized permeate flow drops 15%. Our field data shows plants that dose antiscalant correctly extend membrane life by 24-36 months.

Biological Fouling and Biofilm Growth

Warm feed water above 25°C in an osmosis drinking water system, combined with insufficient chlorination, creates perfect conditions for bacterial colonies. Biofilm produces thick slime that increases pressure drop and creates dead zones where chlorine cannot penetrate.

Fix: Maintain free chlorine at 0.5-1.0 mg/L at the carbon filter inlet, followed by complete dechlorination before the RO membrane. Shock-dose with non-oxidizing biocide (DBNPA) every 4-6 weeks. Our engineers recovered a Peruvian bottled water plant from 42% to 68% recovery in just three days using this exact protocol.

Pre-filter Clogging and Channeling

A Silt Density Index (SDI) above 4 destroys membrane performance within weeks. Many plants mistakenly extend cartridge filter life to save money, causing channeling and particle breakthrough.

Fix: Replace 5-micron cartridges when differential pressure reaches 1.0 bar—never exceed 1.4 bar. Install automatic backwash multi-media filters upstream for feed water with SDI > 3. Plants that follow this rule maintain SDI below 2.5 for years.

Water Quality Problems That Trigger Immediate Customer Complaints

These issues affect final product safety and force production halts until resolved.

Sudden Increase in Permeate Conductivity

Usually, a sudden rise in permeate conductivity, like going from 10 µS/cm to 80 µS/cm in one night, means that there is mechanical damage in the reverse osmosis system. O-ring failure, cracked end caps, or glue-line leaks in the pressure vessels are common reasons why the membrane doesn't work properly and salt can get through. To fix this, you should do a probe test where you put air at 2 bar into each vessel separately and watch the permeate conductivity. The faulty tube will show a conductivity spike right away. Once you know which O-ring or end cap is broken, you should replace it right away. To keep downtime to a minimum, make sure that emergency response teams have full replacement kits that work with all standard 8-inch vessels. This way, repairs can be done quickly, and the system can start working again.

Chlorine Attack on Polyamide Membranes

When carbon filters in an osmosis drinking water system are full and can't get rid of any more chlorine, the polyamide membranes become oxidized in a way that can't be fixed. As the barrier material breaks down, salt rejection usually drops quickly, from 99% to below 90% in just a few days. Set a high alert level of 150 mV for constant Oxidation-Reduction Potential (ORP) tracking after the carbon filter in the osmosis drinking water system to stop this from happening. Also, change the carbon media in the osmosis drinking water system before it runs out at 70% of its maximum capacity instead of waiting until it is completely empty. Once chlorine damage has happened, the membranes in the osmosis drinking water system can't be fixed; they need to be completely replaced to get the rejection rates back to normal and make sure the **osmosis drinking water system** works well in the long run.

Mechanical and Electrical Failures That Stop Production Completely

High-Pressure Pump Damage

Operating the pump without liquid (dry running), experiencing cavitation, or encountering bearing failure will trigger an immediate system shutdown. The Shimge multi-stage pumps we utilize provide early indications of potential issues through abnormal increases in vibration and elevated current consumption. To mitigate such risks, it is essential to install a low-pressure protection switch that automatically cuts off power when the feed pressure drops below 0.5 bar, along with a high-current protection relay. Additionally, ensure that pump vibration remains under 4.5 mm/s during operation. As part of our comprehensive service agreements, quarterly laser alignment and thorough bearing inspections are performed, which have proven to prevent over 90% of pump-related failures by addressing misalignment and wear before they escalate.

Control Valve Malfunction (Runxin Valves)

When automatic valves in the osmosis drinking water system become stuck in an incorrect position, they disrupt normal system operation of the osmosis drinking water system, leading to either no permeate flow or complete bypass, both of which impact process efficiency. The primary cause of such malfunctions is scale accumulation inside the valve body, which restricts movement and interferes with proper sealing. To resolve this, we recommend scheduling an annual disassembly and mechanical descaling of all Runxin multi-port valves in the osmosis drinking water system. During maintenance, apply food-grade silicone grease to all moving components to ensure smooth operation and extend service life. Our trained technicians can efficiently complete this preventive service for the osmosis drinking water system within four hours during planned maintenance windows, minimizing downtime and maintaining valve reliability.

Bearing Failure and Cavitation Prevention

Bearing failure and cavitation represent two major threats to high-pressure pump integrity, often resulting in sudden operational stoppages. These issues can be detected early through monitoring systems that track unusual vibration patterns and rising electrical current draw in Shimge multi-stage pumps. To prevent such damage, install protective devices such as a low-pressure cutoff switch set at 0.5 bar and a high-current relay. Vibration levels should be consistently maintained below 4.5 mm/s. Our service contracts include quarterly laser shaft alignment and detailed bearing inspections, which together help avoid nearly 90% of pump failures by ensuring optimal operating conditions and early detection of mechanical defects.

FAQ

1. What causes a sudden drop in recovery rate from 68% to 45%?

A sudden and significant decline in the system recovery rate, such as dropping from 68% to 45%, is most frequently attributed to one of two primary mechanical issues. The most common culprit is a malfunctioning concentrate (reject) control valve that has become stuck in an overly open position, forcing too much water to waste instead of being recovered. Alternatively, severe scaling, particularly within the last stage's membrane elements, can physically block flow paths and drastically reduce permeate production. To diagnose this, first physically inspect and verify the valve's operational position. If the valve is functioning correctly, the next step is to perform a system normalization calculation. This process compares current operating data to baseline performance, isolating the impact of temperature and pressure; a confirmed reduction in normalized permeate flow strongly indicates a scaling problem that requires immediate cleaning.

2. How do I know if my membranes are scaled or fouled?

Differentiating between scaling and fouling is critical for applying the correct cleaning procedure, and they present distinct symptom profiles. Scaling, which is the precipitation of inorganic salts like calcium carbonate or sulfate, typically leads to a noticeable increase in the differential pressure across the membrane vessel. However, the salt rejection capability often remains relatively stable and high. In contrast, fouling—caused by organic matter, silica, or biological substances—also increases differential pressure but is accompanied by a significant and clear decrease in salt rejection. The most definitive diagnostic method is to conduct sequential cleaning trials. Start with an acidic clean; if performance metrics like flow and pressure drop improve, it confirms scaling. If not, proceed with an alkaline cleaning, which is effective at removing organic and biological foulants, to identify the nature of the blockage.

3. Can I repair a damaged RO membrane myself?

No, it is not possible for an operator to repair a physically or chemically damaged reverse osmosis membrane. The high-performance polyamide layer, which is an extremely thin and delicate film responsible for achieving 99% salt rejection, is irreversibly compromised by chemical oxidants (like chlorine), extreme pH exposure, or mechanical abrasion. Once this dense polymer layer suffers damage, its microscopic structure is permanently altered, and its performance cannot be restored to the original factory specification through any cleaning or field remediation technique. The loss of salt rejection is permanent. The only solution to re-establish guaranteed system performance, particularly the critical 99% rejection rate, is the complete replacement of the damaged membrane elements with new ones.

Reliable Osmosis Drinking Water System Supplier for Industrial Projects | Morui

Guangdong Morui Environmental Technology Co., Ltd. has solved every problem listed above in real osmosis drinking water system operating plants across three continents. With our own membrane factory, multiple equipment assembly plants, 20 full-time RO engineers, and 14 branches, we guarantee response times others cannot match.

Send your current water analysis and operating data to Benson Lai at benson@guangdongmorui.com today. Our senior engineers will identify hidden problems in your system and deliver a detailed correction plan plus firm quotation within 24 hours – completely free of charge.

References

1. American Membrane Technology Association. Fouling and Cleaning in Reverse Osmosis Systems, 2022.

2. Desalination Journal. Volume 512, 2021 – Biological fouling prevention strategies in full-scale RO plants.

3. U.S. EPA. Technical Development Document for Reverse Osmosis Systems, 2020.

4. International Water Association. Scaling and Antiscalant Performance in Brackish Water Desalination, 2023.

5. Journal of Water Process Engineering. Volume 49, 2022 – Chlorine damage mechanisms in polyamide RO membranes.

6. World Health Organization. Safe Drinking-water from Desalination, Technical Report 2019.