How to Change Reverse Osmosis Filters and the Membrane
Article Summary: To change RO filters, identify the correct replacements, shut off the supply and tank, release pressure, and replace the appropriate cartridges. Check seals, restore water, inspect for leaks, and complete your model’s flushing instructions before use. This guide covers conventional housings, a separate membrane, and an inline postfilter; quick-change and tankless systems may need different procedures.
Go straight to: Cartridge filters · RO membrane · Inline postfilter · Restart and flush
Before You Start: Match Your RO System
This guide covers conventional under-sink RO systems with screw-off housings. Match your system to the examples below and find its owner’s manual before starting.
Twist-on, sealed, or tankless system? Use its model-specific replacement procedure; do not open sealed cartridges.
3-stage: 2 housings + membrane
4-stage: 2 housings + membrane + inline filter
4-stage: 3 housings + membrane
5-stage: 3 housings + membrane + inline filter
Find the Right RO Replacement Filters
Select your system type, brand, and model to find matching filters and parts. Check whether a kit includes only sediment and carbon filters or also includes the membrane.
Find My RO Replacement Filters
No model label? Get help identifying your RO system.
Which Type of RO Filter Are You Replacing?
These are examples, not a replacement set. Select parts by system brand and model.
Sediment Prefilter
5-micron, 2.5 × 10-inch sediment cartridge for compatible housings. Use the cartridge replacement steps below.
Sealed RO Membrane
50 GPD Q-Series membrane with flow control.
Sealed assembly: follow your model’s instructions. Do not open it or use the loose-membrane procedure below.
Inline Carbon Filter
2 × 10-inch inline carbon filter with 1/4-inch female threads. Confirm your fittings and the filter’s flow direction.
Where is the carbon prefilter? Conventional RO systems may have both sediment and carbon cartridges in the lower housings. Sediment filters trap particles; carbon prefilters reduce chlorine before water reaches the membrane. They have different jobs—keep each in its specified stage. Find the correct carbon cartridge through the Replacement Filter Finder.
How Do 3-, 4-, and 5-Stage RO Filter Changes Differ?
Replace parts by their function and connection style, not stage count alone. For the conventional layouts illustrated above, use the cartridge, membrane, and inline-filter instructions as applicable. Replace only the stages due for service.
Not sure what each stage does? See how a reverse osmosis system works.
| Layout shown | Parts and replacement sections |
|---|---|
| 3-stage: two vertical housings and a membrane | Use the cartridge steps for the prefilters and membrane steps when the membrane is due. |
| 4-stage: two vertical housings, membrane, and inline filter | Use cartridge, membrane, and inline postfilter sections as applicable. |
| 4-stage: three vertical housings and a membrane | Use the cartridge steps for all three prefilter housings; follow the membrane section when due. |
| 5-stage: three vertical housings, membrane, and inline filter | Use cartridge steps for the prefilters, membrane steps when due, and the inline section for the polishing filter. |
Prepare and Shut Down the System
Gather the correct replacements, a shallow pan, towels, and a compatible housing wrench if needed. Wash your hands, clean the work area, and keep new filters packaged until installation.
First filter change? Photograph your system and tube connections. Lay out replacements in stage order and work on one stage at a time.
Find these four details in your manual:
- The correct cartridge order and part numbers.
- Housing tightening instructions and approved O-ring lubricant.
- Whether carbon prefilters need flushing before reconnecting the membrane.
- Startup flushing and any membrane tank fill-and-discard cycles.
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Step 1: Record filter positions
Note cartridge part numbers, tubing connections, and filter locations before removal. Keep parts in the correct stage order.
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Step 2: Shut off the supply
Close the RO feed-water valve. Follow the manual for switching off any booster pump or other powered components.
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Step 3: Close tank and appliance lines
Close the storage-tank valve and any separate refrigerator or ice-maker line. Follow the valve markings rather than assuming every handle operates identically.
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Step 4: Release pressure
Open the RO faucet and allow flow to stop before loosening housings or tubing. Put a shallow pan and towels under the system to catch remaining water.
Cleaning and Sanitizing Are Different
Washing empty housings is not a complete sanitizing procedure. If sanitizing during filter service, follow the model instructions and current sanitizer label before installing new cartridges. Our RO sanitizing guide explains when filters and membranes must be removed and how to flush afterward.
How to Replace Reverse Osmosis Filter Cartridges
Before opening anything: shut off the feed and tank, then release pressure. Complete the preparation and shutdown steps.
Use these steps for sediment and carbon cartridges in reusable, screw-off housings.
Know the parts: The housing is the reusable cup; the cartridge is the filter you replace. The O-ring seals the cup to the fixed head. This diagram shows the parts separated, not to scale.
See a close-up: how the O-ring sits in its groove
Check before reassembly: the correct O-ring should sit evenly in its groove, with no twists or raised sections. Replace a damaged seal and use only the lubricant specified for your system.
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Step 1: Remove housings and used cartridges
Keep a pan and towel underneath. Unscrew the lower housing cup from the fixed head, using its compatible wrench if needed. Support the assembly and avoid stressing tubing. Keep track of which cartridge belongs in each position.
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Step 2: Clean empty housings
Remove the cartridge and housing O-ring as directed. Wash the empty housing with warm water and soap, then rinse away all residue. Complete any separate sanitizing procedure required by the manual.
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Step 3: Inspect and reseat O-rings
Check for cuts, nicks, or damage; replace damaged seals with the correct parts. Apply the manufacturer-approved lubricant as directed and seat each O-ring evenly in its groove.
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Step 4: Confirm replacement parts
Check the system model and cartridge part number before unwrapping. Similar size or appearance alone does not establish compatibility.
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Step 5: Fit the new cartridges
Seat each cartridge in its specified housing. Reattach the housing and tighten according to the manual without overtightening.
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Step 6: Complete the required stages
Repeat for remaining prefilters. Follow any instructions to flush new carbon cartridges before reconnecting the membrane. Replace the membrane or inline filter only when due, using the sections below.
How to Replace an RO Membrane
Before opening anything: shut off the feed and tank, then release pressure. Complete the preparation and shutdown steps.
This procedure is for a loose membrane inside a reusable housing. Sealed or quick-change assemblies need their own instructions.
Check the orientation: In the conventional design shown, the small O-ring end enters first and the large seal stays near the cap. Confirm the orientation in your membrane instructions.
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Step 1: Disconnect cap-side tubing
Identify the membrane housing and note its connections. Remove tubing from the housing cap. For collet-release fittings, see how to disconnect John Guest tubing.
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Step 2: Open the housing and remove the membrane
Unscrew the cap, keeping its seal safe. Note the old membrane’s orientation. Use needle-nose pliers if needed to grip the used element, taking care not to damage the housing.
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Step 3: Install the specified replacement
Check the housing and seals. For conventional elements, the small O-ring end goes into the housing first and the large brine seal is toward the cap; confirm this against the membrane instructions. Seat it fully without forcing incompatible parts.
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Step 4: Reconnect the cap and tubing
Reseat the cap seal and tighten as directed. Push quick-connect tubing to the fitting’s internal stop, then pull gently to confirm it holds.
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Step 5: Follow membrane startup requirements
Complete the membrane manufacturer’s flushing and tank fill-and-discard procedure before drinking the water. Use the restart and flushing checklist below.
Inline Polishing Filter Replacement Instructions
Before opening anything: shut off the feed and tank, then release pressure. Complete the preparation and shutdown steps.
Match the new filter’s part number, connections, and flow-direction marking.
Check the filter connections: some inline filters have built-in quick-connect ports. The CL10ROT33-BB shown above has threaded ports that take separate adapters. Follow the filter and adapter instructions for sealing and tightening threaded connections.
How to Release and Reconnect Quick-Connect Tubing
Disconnect
The collet is the release ring around the tube. With pressure released, hold it inward while withdrawing the tube.
Reconnect
Push the correct, undamaged tubing fully into the fitting to its internal stop.
Check the grip
Pull gently to check that the tube holds. Check for leaks when pressure returns.
These illustrations show collet-release connections. See the John Guest fittings guide for tubing preparation and fitting details.
An optional John Guest collet release tool can help press compatible 1/4-inch and 3/8-inch collets when space is tight.
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Step 1: Record direction and disconnect
Note which tube connects to each end and the filter’s flow direction. Disconnect tubes using the appropriate fitting procedure.
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Step 2: Transfer external fittings only when appropriate
Some filters have built-in ports; others use removable threaded adapters. If reusing adapters is permitted, inspect them and follow product instructions for sealing and tightening. Do not apply thread tape to a push-fit tube connection.
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Step 3: Install in the correct flow direction
Connect the replacement according to its flow marking. Fully seat quick-connect tubing to the internal stop and pull gently to check it. Follow the filter’s startup-flush instructions.
Restart, Flush, and Check for Leaks
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Step 1: Restore the feed-water supply
Confirm housings and tubing are reassembled, then reopen the RO supply according to the manual. Keep tank and appliance lines in the positions specified for startup.
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Step 2: Check serviced connections
Inspect housings, caps, seals, and tubing as pressure returns. If a leak appears, shut off the supply and release pressure before correcting it. Do not try to stop a leak by overtightening a housing.
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Step 3: Flush as specified
Complete the specified cartridge flush and any membrane tank fill-and-discard cycles. Discard flushing water and keep appliance lines isolated until the required flush is complete.
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Step 4: Return tank and appliance lines to service
Open the tank valve at the stage specified in your manual. Complete refill and discard cycles before drinking or reconnecting the refrigerator/ice maker. Recheck for leaks.
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Step 5: Record the service date
Note replaced parts and next service dates. For persistent low flow, see slow RO water flow or tank not filling.
Before Drinking the Water
- Flushing complete: required rinses and tank-discard cycles are finished.
- Connections dry: inspect serviced housings, caps, and fittings under operating pressure.
- Valves set: feed, tank, and appliance valves are in the operating positions specified for your system.
- Service recorded: note the date, replaced parts, and next replacement dates.
RO System Not Working After a Filter Change?
Start with the parts you just serviced. Confirm compatibility, cartridge placement, tubing connections, valve positions, and completion of the required startup flush. A storage tank can need time to refill. If anything leaks, shut off the supply and release pressure before opening a housing or fitting.
| Problem | What to check |
|---|---|
| Leak at a housing | Check the correct cartridge is seated, the O-ring is undamaged and in its groove, and the housing is reassembled correctly. Do not overtighten to compensate for a damaged seal. |
| Leak at a tubing connection | Check for a square, undamaged tube end, correct size, and full insertion to the fitting’s tube stop. See John Guest connection guidance. |
| Low flow or no water | Check the feed and tank valves, kinked tubing, correct parts, and the refill/startup stage. See slow RO flow and tank not filling. |
| Problems persist | Keep a leaking system shut off and contact ESP support with the system model, replaced part numbers, and your order number if available. |
When Should You Change RO Filters and the Membrane?
Use your model’s schedule first. ESP’s general guidance below is a starting point; intervals depend on the product, water conditions, and usage.
| Component | General replacement guidance |
|---|---|
| Sediment and carbon prefilters | Often every 6–12 months; follow the specific model’s schedule and water-condition requirements. |
| RO membrane | ESP’s general guide recommends around 24 months; some models specify different intervals. Follow the manual and its performance checks. |
| Carbon polishing/postfilter | Commonly every 12 months, subject to model instructions. |
See RO maintenance guidance and find your owner’s manual. Taste alone does not establish filter or membrane performance.
RO Filter and Membrane Replacement FAQs
Are RO replacement filters universal?
No. Stage count and appearance alone do not confirm a match. Check your brand, model, cartridge part numbers, and connection requirements. Use the Replacement Filter Finder or ask our team before ordering.
Do I replace the membrane every time I change RO filters?
Not necessarily. Prefilters, postfilters, and membranes can have different service intervals. Replace the stages due according to your model’s schedule and performance checks. Confirm whether your kit includes the membrane.
What if a filter housing is difficult to open?
Confirm the feed and tank are shut off and system pressure is released. Use the correct housing wrench and support the assembly. Do not force or crack the housing. If it still will not open, ask for help.
How long should I flush after changing RO filters?
Flushing requirements depend on your system and the parts replaced. Check the cartridge and membrane instructions for rinse duration and any tank fill-and-discard cycles. Finish the specified flush before drinking or reconnecting an ice maker.
Should I sanitize when changing RO filters?
Follow your model’s maintenance instructions. ESP recommends sanitizing during appropriate filter service. Use the RO sanitizing guide and current sanitizer label; keep new filters packaged until sanitizing and its flushing steps are complete.
Why is water flow slow after replacing filters?
Check that correct parts are installed, tubing is not kinked, valves are in their normal positions, and required flushing is complete. The tank may need time to refill. See slow RO water flow rather than assuming the membrane needs replacing.
Ready to Find Your Replacement Filters?
Find RO replacement filters and membranes and model-specific kits by system brand and model. Check what each kit includes before ordering.
Find My RO Replacement Filters
Need installation help with filters purchased from ESP Water? Have your order number ready and contact our US-based team: 1 (877) 377-9876, Monday–Friday, 8 AM–5 PM CT.
