Laboratory pure water purifiers are essential equipment for providing high-purity water for chromatographic analysis, experimental preparation and instrument cleaning, whose stable operation directly guarantees the accuracy of laboratory test data. The fault of continuous water production and uninterrupted wastewater discharge is one of the most common operational failures of reverse osmosis (RO) water purifiers. Under normal working conditions, the equipment will automatically stop water production and close the wastewater pipeline when the water tank is full. Once the fault occurs, the machine keeps running, produces water continuously and discharges wastewater nonstop, which not only causes serious water resource waste and increases equipment power consumption, but also accelerates the aging of filter elements and RO membrane, and even leads to pipeline pressure overload and secondary equipment faults. This document systematically analyzes the three core causes of this common fault and puts forward targeted and practical solutions for daily laboratory equipment maintenance.
The first core cause is the failure of the high-pressure switch, which is the most frequent inducement of continuous water production and wastewater discharge. The high-pressure switch is responsible for sensing the water pressure inside the pure water tank. When the tank is full and the pressure reaches the preset threshold, the switch will automatically disconnect the circuit and send a stop signal to the water purifier to terminate water production. After long-term operation, the switch is prone to spring fatigue, internal contact oxidation and sensor sensitivity decline. In this case, even if the water tank is full and the pressure meets the standard, the switch cannot accurately identify the pressure signal and fails to trigger the shutdown program, resulting in the machine continuing to operate and discharge wastewater. In addition, pipeline pressure fluctuation and scale deposition on the switch probe will also interfere with pressure sensing and cause misjudgment.
The corresponding solution for high-pressure switch failure is standardized inspection and replacement. First, cut off the power and water supply of the equipment for safe operation, disassemble the high-pressure switch installed on the pure water pipeline, and clean the surface scale and sediment of the probe with pure water and soft brush to eliminate sensing interference. Then conduct pressure test detection: manually pressurize the pipeline to the standard shutdown pressure, and observe whether the switch can bounce and disconnect the circuit normally. If the switch responds sluggishly, cannot reset automatically or fails to trigger shutdown, it indicates internal spring and contact damage, and the original switch must be replaced with a matched original high-pressure switch. After replacement, debug the pressure threshold to ensure the equipment can stop water production accurately when the water tank is full.
The second main cause is RO membrane blockage and fouling aging. The RO membrane is the core filtration component of the water purifier, undertaking the task of intercepting impurities, heavy metals and microorganisms. Long-term use will lead to the accumulation of scale, colloids and organic pollutants on the membrane surface and internal pores, causing serious membrane blockage and flux attenuation. The blocked RO membrane cannot normally infiltrate pure water into the water tank, resulting in insufficient internal water pressure. The high-pressure switch cannot reach the shutdown pressure value, so the equipment will keep running to produce water and discharge wastewater in a circulating manner. Different from sudden faults, this problem is progressive. The wastewater discharge volume will gradually increase with the aging of the membrane, and the pure water production efficiency will decrease significantly.
The solution for RO membrane fouling and blockage is regular cleaning and replacement. For slightly polluted and blocked RO membranes, professional membrane cleaning agent can be used for circulating cleaning to dissolve surface scale and organic deposits, restore membrane permeability and water flux. For severely aged and blocked membranes with reduced filtration performance and failed cleaning recovery, the RO membrane element must be replaced in time. After replacement, flush the pipeline thoroughly to discharge residual cleaning agent and impurities, and test the water production and wastewater discharge ratio. Standard pure water purifiers have a fixed water-waste ratio; after debugging, the equipment can automatically stop running when the water tank is full, and the fault can be completely eliminated.
The third key cause is floating valve failure of the pure water tank. The floating valve controls the water storage limit of the water tank through buoyancy induction. When the water tank is full, the floating valve rises to close the water inlet pipeline, cutting off the water production cycle. Long-term water immersion and impurity adhesion will cause the floating valve to be stuck, inflexible in lifting, or the sealing ring to age and leak. If the floating valve cannot rise in place or fails to seal tightly, the water tank will always be in a water-deficient pressure state. The equipment will continuously produce water to supplement the tank, and the wastewater pipeline will keep discharging water synchronously. This fault is often misjudged as pipeline pressure failure, resulting in delayed maintenance.
The targeted solution for floating valve failure is disassembly, cleaning and maintenance. First, drain the water in the pure water tank, take out the floating valve assembly, clean the surface attachments, scale and sticky impurities that cause jamming, and check the flexibility of the floating rod. Replace the aging and deformed sealing rubber ring to eliminate water leakage. After maintenance, reinstall the floating valve and conduct water injection test to verify that the floating valve can rise and fall flexibly and seal tightly. If the floating rod is deformed or the internal structure is damaged and cannot be repaired, replace the floating valve assembly entirely to ensure normal water level limit control.
In summary, the continuous water production and wastewater discharge fault of water purifiers is mainly caused by high-pressure switch failure, RO membrane blockage aging and water tank floating valve failure. Laboratory maintenance personnel should conduct targeted inspection according to fault characteristics, eliminate faults in time, and establish a daily maintenance mechanism including regular cleaning of filter elements, membrane components and valve parts. Standardized maintenance can not only solve common running faults, reduce water and power waste, but also effectively extend the service life of water purifiers and ensure the stable supply of qualified pure water for experimental work.
