2026 How to change reverse osmosis filters？
The stable operation of a Reverse Osmosis filter directly determines the quality of the produced water. Whether in the electronics, chemical, pharmaceutical, or food processing industries—among others—should the filter encounter issues such as clogging or performance degradation, it would not only result in reduced water production efficiency and substandard water quality but could also trigger a cascade of consequential losses, including accelerated wear on downstream equipment and production downtime.
This article will provide a detailed breakdown of the replacement process, assessment criteria, operational protocols, and key considerations for reverse osmosis filters, with the aim of extending the service life of the equipment.
1. Determining the Appropriate Time to Replace Each Component of Reverse Osmosis Filters
An reverse osmosis filter is not a standalone component, but rather a complete system comprising pre-treatment filter cartridges, reverse osmosis membrane elements, and post-purification filter cartridges. Consequently, the functions, replacement cycles, and operational procedures for these various components differ significantly. Due to a lack of specialized knowledge, many enterprises blindly replace filter cartridges or membrane elements, a practice that risks damaging the core components of the equipment.
First, we must clearly define the criteria for determining when to replace each component, in order to avoid the waste caused by premature replacement or the equipment failures triggered by delayed replacement.
1. The pre-treatment filter cartridges primarily consist of PP cotton filters and activated carbon filters. The PP cotton filter is responsible for intercepting large particulate impurities—such as sediment, rust, and colloids—present in the raw water, thereby protecting downstream precision components. The indicators for replacing this filter are quite intuitive: replacement is required immediately if the device's inlet water pressure drops by 5–10%, the water output decreases significantly, or the surface of the filter cartridge appears yellowed or blackened. The standard replacement cycle is 3 to 6 months. However, if the raw water turbidity is high or the equipment operates continuously for 24 hours, this interval should be shortened to 1 to 2 months.
2. Activated carbon filters are designed to adsorb residual chlorine, organic matter, and substances causing discoloration or odors in the water, thereby preventing residual chlorine from oxidizing and damaging the reverse osmosis membrane. Replacement is required ahead of schedule if the treated water develops a slight odor, its taste deteriorates, or if the residual chlorine content in the water is detected to exceed 0.1 mg/L. The standard replacement cycle for this filter is 6 to 12 months.
3. The replacement cycle for the reverse osmosis (RO) membrane element is relatively long, typically ranging from 1 to 3 years under standard usage conditions. However, the actual need for replacement must be determined based on specific treated water parameters: immediate replacement is required if the water output drops by more than 30%, the TDS value of the treated water doubles, or if the membrane housing leaks or the inter-stage pressure differential exceeds permissible limits. The specific replacement schedule should ultimately be adjusted based on the quality of the raw water, operating pressure, and maintenance practices.
4. The post-activated carbon filter primarily improves the taste of the purified water. Its replacement cycle is 12 to 18 months. It is recommended to replace it simultaneously with the Reverse Osmosis membrane to ensure consistent water quality.
2. Preparation for Replacing Reverse Osmosis Filters
The preparatory work for reverse osmosis filters directly impacts operational efficiency and safety. Therefore, we must make advance preparations regarding tools, materials, and safety equipment.
① Tools: You will need to prepare specialized filter housing wrenches, adjustable wrenches, pipe wrenches, screwdrivers, and similar tools to facilitate the removal of filter housings, membrane housing end caps, and pipe fittings.
② Materials: You must prepare new filter cartridges and reverse osmosis membrane elements that are compatible with the specific equipment model. Additionally, have on hand auxiliary supplies—such as PTFE tape, food-grade silicone-based lubricant, and spare O-rings—to prevent interruptions during the replacement process caused by incompatible parts or missing materials.
③ Safety Precautions: Operators must wear non-slip gloves and safety goggles to protect against potential injuries caused by high-pressure water jets, chemical residues, or sharp components.
④ Furthermore, you must close the equipment's inlet valve and shut off the power supply to the high-pressure pump. Open the product water faucet or pressure relief valve to discharge the pressure within the piping. Commence disassembly only after confirming that the pressure gauge reads 0 MPa. For large-scale industrial systems, it is also necessary to record the operating parameters prior to the replacement to facilitate subsequent comparison and system commissioning.
3. Operating Procedures for Reverse Osmosis Filters
When performing replacement procedures, we must adhere to the sequence of "pre-treatment first, followed by the core membrane, and finally post-purification." Operations should be conducted step-by-step and in accordance with established protocols to prevent operational errors that could damage the equipment.
The replacement process for the pre-treatment PP cotton and activated carbon filter cartridges is relatively straightforward: First, use a filter wrench to unscrew the filter housing in a counter-clockwise direction. Note that residual water will remain inside the housing. Use a container to catch this water to prevent spills from soiling the work area. After removing the old filter cartridge, rinse the inner walls of the housing with clean water. If moss or stubborn impurities are present, use a soft-bristled brush to gently clean them away. Properly insert the new filter cartridge into the housing. The PP cotton cartridge has no specific orientation requirements, whereas the activated carbon cartridge requires proper alignment of the inlet and outlet ends (which are typically marked with "IN" and "OUT" labels on the cartridge). Wrap 2–3 turns of PTFE thread seal tape around the threads of the filter housing interface, then screw the housing back on in a clockwise direction. Apply moderate force when tightening to avoid damaging the threads by overtightening, or causing leaks due to insufficient tightness.
Replacing the reverse osmosis (RO) membrane element is a critical step that requires extreme caution during operation. First, locate the membrane housing. In industrial equipment, these housings are typically cylindrical with end caps at both ends, some of which bear an "RO Membrane" label. Use a wrench to unscrew the end caps at both ends of the housing. It is recommended to loosen the concentrate outlet end first, followed by the feed water inlet end, to prevent residual water from spraying out and causing injury. When removing the old membrane element, use a specialized pull rod or apply gentle pressure to push it out, taking care to avoid bending or scratching the membrane surface. Once removed, inspect the surface condition of the membrane to make a preliminary assessment of the type of fouling present. This provides a basis for optimizing subsequent pretreatment processes. The old membrane must be disposed of in accordance with hazardous waste regulations and must not be discarded indiscriminately.
Before installing the new membrane element, flush its surface with low-pressure water to remove the protective solution applied during manufacturing. Apply a thin, even layer of food-grade silicone-based lubricant to the O-rings located at both ends of the membrane element to prevent them from being scratched during installation. Carefully insert the new membrane into the housing, strictly adhering to the designated direction of water flow. The "Inlet" indicator on the membrane element must align with the feed water inlet direction of the housing to ensure a tight seal between the O-rings and the inner wall of the housing. When reattaching the housing end caps, verify that the O-rings are intact, align the caps with the ports, and tighten them slowly to avoid applying excessive force that could deform the O-rings. For large-scale systems featuring multiple membrane housings connected in series, install the elements sequentially—following the flow path from the initial feed inlet to the final concentrate outlet—to ensure tight connections between adjacent membrane elements.
Replacing the post-filtration activated carbon cartridge is a relatively simple process, involving two common types: push-fit and threaded. For the push-fit type, simply press down on the interface release tab, pull out the old cartridge, and insert the new one until you hear a distinct "click." For the threaded type, unscrew the old cartridge in a counter-clockwise direction. Then, wrap a small amount of PTFE thread seal tape around the threads of the new cartridge and screw it in clockwise, ensuring a leak-free connection.
4. Commissioning After Replacing Reverse Osmosis Filters
Upon completion of the replacement process, the Reverse Osmosis System must undergo commissioning and inspection to ensure proper operation.
First, open the inlet valve, power on the unit, and open the product water faucet and concentrate valve. Allow the system to run for 5–10 minutes to purge air and residual impurities from the piping. The initial product water may appear turbid, which is a normal occurrence. Subsequently, inspect the interfaces of the filter housings, the end caps of the membrane housings, and all pipeline connections for any signs of leakage. If any leaks are detected, immediately shut down the system, depressurize it, and retighten the connections or replace the sealing rings. After 30 minutes of operation, measure the product water TDS value, product water flow rate, and system pressure differential. Compare these readings against the parameters recorded prior to the replacement to confirm that the system has returned to its normal operating range. If the product water quality fails to meet the required standards, verify that the filter cartridges are installed in the correct orientation, that the membrane elements are properly sealed, and that there are no malfunctions within the pretreatment system.
5. Summary
The replacement of reverse osmosis filters must adhere to the principles of "precise assessment, thorough preparation, standardized operation, and rigorous commissioning." By flexibly adjusting the process based on the actual operating conditions of the equipment, the purification efficiency of the reverse osmosis system can be fully realized, thereby ensuring a stable and compliant supply of process water for industrial production.