Reverse Osmosis Secondary Multi Way Valve Control Purified Water Equipment

Core Working Principle

1. Pretreatment stage: Raw water passes through the pre-filter system (PP melt-blown filter + activated carbon filter + precision filter) to remove suspended solids, rust, residual chlorine, organic matter, and fine particles, ensuring the inlet water quality of the RO membrane meets the standard and preventing membrane pollution/scaling.
2. Primary RO desalination stage: The pretreated water is pressurized by a high-pressure pump to reach the osmotic pressure required for reverse osmosis, and enters the primary RO membrane module. The primary RO membrane intercepts about 97~99% of dissolved salts, bacteria, viruses, and colloids, and the produced primary pure water (conductivity generally ≤10μS/cm) is sent to the secondary RO system, while the concentrated water is discharged or partially recycled under the control of the multi-way valve.
3. Secondary RO deep purification stage: The primary pure water is pressurized by a secondary high-pressure pump (low pressure, lower than the primary pump) and enters the secondary RO membrane module. The secondary RO membrane performs deep desalination and impurity interception on the already purified primary pure water, removing the trace salts and impurities remaining in the primary RO produced water. The secondary pure water has extremely low conductivity (generally ≤1μS/cm, even up to 0.1~0.5μS/cm for high-standard configuration), which is the final qualified pure water; the small amount of concentrated water produced by the secondary RO is returned to the primary RO inlet water side under the control of the multi-way valve for recycling, improving the overall water recovery rate of the equipment (up to 70~85%).
4. Multi-way valve control core: The multi-way valve is an integrated hydraulic control component with multiple water inlets/outlets and switching functions. It is connected to the pretreatment, primary RO, and secondary RO units, and realizes one-key switching of the equipment’s working conditions:
   • Water production condition: The multi-way valve connects the whole purification pipeline, and raw water flows through each unit in turn to produce pure water stably;
   • Flushing condition: When the equipment is started/shut down or runs for a certain time, the multi-way valve switches the pipeline to introduce raw water/pure water to flush the primary/secondary RO membrane surfaces, removing the impurities adsorbed on the membrane and preventing membrane blockage;
   • Backwashing condition: For the pretreatment filter core/ membrane, the multi-way valve reverses the water flow direction to backwash the filter material, and discharge the intercepted impurities, extending the service life of pretreatment consumables;
   • Pressure/flow regulation: The multi-way valve adjusts the opening degree of the concentrated water discharge port in real time to control the operating pressure of the primary/secondary RO system and the discharge flow of concentrated water, ensuring stable water production and desalination efficiency.

Main Component System (Valve-Core Integrated Design)

1. Raw Water Intake Unit

• Raw water pump, pressure gauge, and water flow meter: Provide stable water pressure/flow for the whole equipment, and monitor the raw water intake parameters in real time;
• Water inlet solenoid valve: Cooperate with the multi-way valve to realize automatic on/off of raw water intake, and link with the pure water tank liquid level for interlock control.

2. Pretreatment Purification Unit (RO Membrane Protection Core)

• 5μm PP melt-blown filter: Remove large particle impurities (sand, sediment, rust) in raw water to prevent scratching the RO membrane;
• Granular activated carbon (GAC) filter: Adsorb residual chlorine, color, odor, and small molecular organic matters in water (residual chlorine will oxidize and damage the RO membrane);
• 1μm precision filter: Further remove fine suspended solids and colloids, ensuring the SDI (Silt Density Index) of RO inlet water ≤5, meeting the RO membrane operation requirements;
• Automatic scale inhibitor dosing device: Add food-grade/industrial scale inhibitor to the pretreatment effluent to prevent calcium/magnesium ions from scaling on the RO membrane surface, Cooperate with the multi-way valve to control the dosing flow.

3. Core Control Unit – Multi Way Valve Assembly

• Integrated multi-way valve (manual/auto optional): The “brain” of the equipment, with multiple hydraulic interfaces connected to pretreatment, primary RO, secondary RO, and concentrated water pipelines; supports manual one-key operation or automatic switching by the controller, completing water production, flushing, backwashing, and concentrated water discharge control;
• Valve control panel/PLC controller: For automatic multi-way valve, it is equipped with a microcomputer/PLC controller, which can set the flushing/backwashing time and frequency, and link with pressure/liquid level sensors to realize intelligent control; for manual multi-way valve, it is equipped with a simple control panel for on-site operation.
• Pressure relief valve/ check valve: Auxiliary valves matching the multi-way valve, preventing water hammer impact and reverse flow of pure water/concentrated water, protecting the RO membrane and pump body.

4. Deep Purification Unit – Secondary Reverse Osmosis (RO) System

• Primary/secondary high-pressure pumps: Special high-pressure pumps for RO (the secondary pump has lower lift and pressure), providing the required osmotic pressure for primary and secondary RO membrane modules respectively; the output pressure is adjusted by the multi-way valve;
• Primary/secondary RO membrane modules (low-pressure composite membrane): Adopt low-pressure high-desalination RO composite membrane (the most mainstream RO membrane type), the primary membrane is for primary desalination, and the secondary membrane is for deep purification; the membrane shell is made of stainless steel/FRP, corrosion-resistant and pressure-bearing;
• RO membrane flushing port: Connected to the multi-way valve, the flushing water is introduced to flush the membrane surface regularly to remove membrane surface pollutants.

5. Pure Water Storage & Post-Treatment Unit

• Sealed pure water tank: Food-grade stainless steel sealed tank, storing the secondary RO produced pure water; equipped with a liquid level sensor, which links with the water inlet solenoid valve and multi-way valve to realize automatic start/stop of water production (stop when the tank is full, start when the water level is low);
• Post-treatment device (optional): Configured according to pure water quality requirements, including UV sterilizer (kill residual microorganisms in pure water, prevent secondary pollution), TOC remover (remove trace organic matter, suitable for laboratory/electronic industry), pH adjustment device (adjust pure water pH to neutral, suitable for pharmaceutical/ drinking water), and precision filter (0.22μm) (terminal filtration, ensure pure water cleanliness).
• Pure water delivery pump: Provide stable water pressure for pure water use, deliver the pure water in the tank to the water use point, and cooperate with the multi-way valve to control the delivery flow.

6. Auxiliary Monitoring & Discharge Unit

• Conductivity meter/T D S meter: Installed at the primary RO effluent, secondary RO effluent, and pure water tank outlet, real-time monitoring the salt content of produced water, and the data is displayed on the control panel;
• Pressure/flow sensors: Installed at the inlet/outlet of primary/secondary RO, monitoring the operating pressure and flow of the RO system, and sending an alarm when the pressure is too high/low;
• Concentrated water discharge pipeline: Controlled by the multi-way valve, the primary RO concentrated water is discharged outside, and the secondary RO concentrated water is recycled to the primary RO inlet water side to improve the water recovery rate;
• Acousto-optic alarm device: Alarm for abnormal conditions (low raw water pressure, high RO pressure, unqualified pure water conductivity, low/high liquid level of pure water tank).

Core Product Features

1. Ultra-high pure water quality, stable deep desalination

   The secondary reverse osmosis process realizes two-stage desalination and purification, the desalination rate is as high as 99.5% or more, the conductivity of produced water is ≤1μS/cm (even lower for high-standard configuration), which is far higher than the single-stage RO equipment, and can meet the quality requirements of laboratory pure water, pharmaceutical preparation water, and electronic ultra-pure water raw water.

2. Multi-way valve integrated control, simple operation

   The multi-way valve replaces the traditional complex pipeline and multiple single valves, reducing the number of pipeline joints and leakage points; manual/auto optional, supporting one-key switching of all working conditions, no professional operation is required, and the operation and maintenance threshold is low (especially suitable for small and medium-sized water use sites such as laboratories and small workshops).

3. High water recovery rate, energy saving and water saving

   The multi-way valve intelligently controls the recycling of secondary RO concentrated water (returned to primary RO inlet), the overall water recovery rate of the equipment is increased to 70~85% (single-stage RO is generally 50~60%), which greatly reduces raw water consumption and is more energy-saving and environmentally friendly.

4. Compact structure, small floor area

   Valve-core integrated modular design, all components are assembled on a stainless steel frame, the pipeline is simplified by the multi-way valve, the structure is compact, the floor area is small (even can be wall-mounted for small models), and it is suitable for installation in small spaces such as laboratories, small workshops, and commercial water stations.

5. Dual protection of RO membrane, long service life

   The multi-way valve realizes regular automatic flushing of primary/secondary RO membranes, and matches with the automatic scale inhibitor dosing device, which effectively prevents membrane pollution and scaling; the secondary RO pump has low pressure, reducing the operating load of the secondary RO membrane, and prolonging the service life of the whole RO membrane system.

6. Intelligent interlock, automatic start/stop

   The automatic multi-way valve is linked with the pure water tank liquid level sensor, pressure sensor, and conductivity meter, realizing automatic start/stop of water production, automatic flushing/backwashing, and automatic alarm for abnormal conditions; no on-site manual duty is required, saving labor costs.

7. Strong adaptability, customizable configuration

   Suitable for raw water such as tap water, groundwater (low salinity/hardness), and reclaimed water (pretreated); the multi-way valve model and RO membrane specification can be customized according to water production capacity (0.1~10m³/h) and pure water quality requirements, and the post-treatment device can be added or reduced flexibly.

Typical Application Scenarios

1. Laboratory water use: Production of laboratory pure water/ultrapure water raw water for universities, research institutes, and testing institutions, meeting the water quality requirements of chemical analysis, instrument testing, and biological experiments;
2. Pharmaceutical & medical field: Production of pharmaceutical preparation water, medical equipment cleaning water, and hospital disinfection water, meeting the GMP standards for pharmaceutical water and medical water quality requirements;
3. Electronic component manufacturing: Production of cleaning water for small electronic components, chips, and semiconductors, requiring low conductivity and low organic matter content of pure water;
4. High-standard drinking pure water: Pure water production for high-end restaurants, hotels, bottled water stations, and family villas, providing high-purity direct drinking pure water;
5. Small industrial production: Pure water production for small workshops such as cosmetics, food processing, and precision electroplating, meeting the process water quality requirements of small-scale production;
6. Indoor small water supply points: Installation in office buildings, research and development centers, and small factories with limited installation space, realizing on-site production of high-purity pure water.

Daily Operation & Maintenance Key Points

1. Multi-way valve maintenance: Regularly check the sealing performance of the multi-way valve interface to prevent water leakage; for manual multi-way valve, apply lubricating oil to the valve core regularly (every 3~6 months) to ensure flexible switching; for automatic multi-way valve, clean the valve core filter screen regularly to prevent blockage.
2. Consumables replacement: Replace the PP melt-blown filter element every 3~6 months, and the activated carbon filter element every 6~12 months (adjust according to raw water quality); the precision filter element is replaced every 6 months.
3. RO membrane maintenance: The multi-way valve is set to flush the RO membrane for 1~2 minutes when starting/shutting down the equipment, and regular backwashing (once every 1~3 days); the RO membrane is replaced every 2~4 years, and the secondary RO membrane has a longer service life due to low operating pressure.
4. Dosing device check: Ensure the scale inhibitor is sufficient, and replace the scale inhibitor in time; check the dosing pump flow regularly to match the raw water intake flow, avoiding insufficient or excessive dosing.
5. Pure water tank maintenance: Clean and disinfect the sealed pure water tank every 6~12 months (use food-grade disinfectant for drinking water), and check the sealing performance of the tank cover to prevent secondary pollution of pure water.
6. Sensor calibration: Calibrate the conductivity meter/TDS meter and pressure gauge every year to ensure the accuracy of monitoring data and the normal operation of the multi-way valve interlock control.

Key Parameter Reference (Common Models)