How to Replace Filters on a Reverse Osmosis (RO) System

RO filters and membranes

How to Install New Reverse Osmosis Filters & Membrane

These instructions are intended for general filter replacement in most standard reverse osmosis (RO) systems and may not be applicable to all RO systems. If your RO system resembles any of the four illustrations below, these instructions should generally be applicable. Whenever possible, refer to the owner’s manual for specific system instructions.

Preparations Before Installing RO Filter Replacements
  • Ensure you have the correct filter cartridges for your specific RO system.
  • Keep filter cartridges in original packaging until they are ready to be installed.
  • Thoroughly wash heads or wear latex gloves when handling new filters.
  • It is recommended to sanitize your RO system when replacing all the filters. Refer to the instruction guidance for more details.
Woman looking at filter installation instructions

Types of Filters on Your RO System

Standard RO systems typically have three types of filters. Follow the specific instructions for each type of filter.

Standard Water Filter Replacement Instructions

standard RO water filtersMost standard RO systems have two or three vertical filters located below the metal bracket. These filters typically include a combination of sediment and carbon block filters.

number 1

Turn Off the Water Supply
Locate the shut-off valve that controls the water flow to your RO system. Turn the valve off to stop the water supply.

number 2

Turn Off Storage Tank
Locate the blue shut-off valve situated on top of the storage tank. Close the valve by turning the blue handle a quarter turn clockwise.

number 3

Turn Off Line to Refrigerator (if applicable)
If there’s a line connecting your RO to your refrigerator or ice maker, locate the shut-off valve on that line. Turn off the valve on the line leading to the refrigerator or ice maker.

number 4

Relieve Pressure
Release any remaining water pressure in your system, by turning on the RO faucet at the kitchen sink and allowing it to run until water stops flowing.

number 5

Prepare for Excess Water
Excess water in the filter housings may spill while replacing filters. Place a shallow tray or pan under the filter housing to catch any water that may spill and have a towel or cloth available.

man holding wrench

Tech Tip: To ensure the new filters get installed in the correct location, identify and note the location of each used filter during removal.

number 6

Remove the Vertical Filter Housings
Identify the two or three (depending on your system) vertical filter housings on your system. Unscrew the vertical filter housings from the system and remove the used filter cartridges. If you encounter difficulty unscrewing the filter housing, you may need a special filter housing wrench.

number 7

Remove O-rings
Carefully remove the O-rings located near the top of each filter housing and place them on a clean surface.

number 8

Disinfect Filter Housings
Thoroughly cleanse the empty filter housings using soap and warm water. Ensure any remaining soap residue is thoroughly rinsed out before inserting the new filter and reattaching.

number 9

Clean and Reseat O-Rings
Wipe the O-rings clean with a soft, clean towel. Inspect them visually for any signs of damage such as nicks, cuts, or abrasions. If any O-ring appears damaged, replace it to prevent potential leaks. If the O-rings are in good condition, lightly lubricate them with silicone lubricant. Insert the O-ring into the filter-housing O-ring groove and ensure it is seated correctly.

number 10

Verify Correct Filters
Before unwrapping the new filters, make sure that they closely resemble the old filters being replaced.

number 11

Install New Filters
Insert each new filter in the correct filter housing. Confirm that the filter is properly seated. Reattach the filter housing to the correct position on the system. Tighten by hand only, avoiding excessive tightening.

RO membrane replacement instrucitons
Number 1

Disconnect Tube from Membrane Housing
Identify the RO membrane filter housing. Disconnect the single tube connected to the membrane housing cap (typically on the right side).

man holding wrench

Tech Tip: Find additional details and how-to video on removing tubing from quick connect fittings here.

Number 2

Remove RO Membrane
Unscrew the cap from the membrane housing and remove the used RO mem-brane. Take note of the direction in which the membrane was installed. If it proves challenging to remove, use needle-nose pliers for assistance.

Number 3

Install New RO Membrane
Insert the new membrane into the housing. Ensure the membrane is properly seated with the large outer rubber stopper closest to the open cap.

man holding wrench

Tech Tip: f you experience resistance while seating the membrane, twist the membrane in a slight circular motion and provide some good pressure to ensure the membrane is fully seated.

Number 4

Reconnect Housing Cap
Securely connect and hand tighten the cap onto the membrane housing.

Number 5

Reconnect Tubing
Insert the tubing into the hole on the housing cap. Push the tubing into the quick connect fitting as far as possible, then pull lightly on the tube to secure grip.

Inline Filter Replacement Instructions
Number 1

Disconnect Tubing
Remove the tubing from each end of the filter, or from fitting connected to each end of the filter.

man holding wrench

Tech Tip: Find additional details and how-to video on removing tubing from quick connect fittings here.

Number 2

External Fittings (if applicable)
If the filter has external fittings attached to each end of the filter, unscrew the fittings from the filter. Remove any remaining plumber’s tape. Wrap male threaded fittings with 2-3 layers of new plumber’s tape and reinstall into the new filter.

Number 3

Connect Tubing to New Filter
Insert tubing into the hole on the new filter. Push the tubing into the quick connect fitting as far as possible, then pull lightly on the tube to secure grip.

Turning on and Testing the RO System
Number 1

Turn on Water Supply
Insert tubing into the hole on the new filter. Push the tubing into the quick connect fitting as far as possible, then pull lightly on the tube to secure grip.

Number 2

Flush the System
Turn on the RO faucet at the sink to initiate the system flush. Ensure that the valve on the storage tank remains closed. This will remove air and carbon fines from the system. Eventually, you should get a small steady stream of water or a very fast drip from the RO faucet. Allow approximately 1-2 gallons flush through the RO system. Place a large bowl or pitcher in the sink to collect the water and help estimate how much water the system has flushed. Discard any collected water.

Number 3

Check the Leaks
While the system is flushing, inspect all connections and filter housings for leaks. Leaks from tubing connections typically indicate tubing was not pushed in far enough. Leaks from housings typically indicate either a damaged O-ring or the housing was not screwed on tight enough.

Number 4

Turn On Storage Tank
Open the ball valve on top of the storage tank by turning the blue handle a quarter turn counterclockwise. The blue handle should be parallel with the tubing connected to the tank.

man holding wrench

Is it Time for a Change?

If your your system is 10 years old or older, it’s time to consider upgrading. We offer a wide assortment of system options, including simple conversion kits, which are a popular, economical option for upgrading your system.

Additional Help

If you purchased your replacement filters from ESP Water Products and require additional help with installation, feel free to reach out to us. You can contact us with your order number at (469) 521-9920 (Monday-Friday 8 am to 5 pm CST) or at

At ESP Water Products, our goal is to make it as easy as possible to replace 1-year annual filter replacement kit RO wateryour RO filters. We provide Replacement Filter Kits for more than 100 RO systems, designed to save you time and money by bundling the necessary annual filter change items together.

If there is no label on your RO system and you're unsure of your system's brand and model, we'll take you through the steps to identify your Reverse Osmosis drinking water system.

RO purified water

When to Change Reverse Osmosis Filters and Membrane

All reverse osmosis systems require periodic maintenance to ensure water quality remains top notch. The most important maintenance for an RO system is on time filter changes. Failure to replace RO filters and membranes on schedule can result in a clogged and damaged system.

Wondering when to change your reverse osmosis filters? Below is the recommended filter and membrane change schedule, as well as step-by-step instructions for how to replace your reverse osmosis water filters.

Sediment prefilter phase

This pre-filter stage is designed to strain out sediment, silt, and dirt and is especially important as the sediment filter protects dirt from getting to the delicate RO membranes that can be damaged by sediment. Learn more about sediment filter. Change this filter every 6-12 months-- more often in areas with very high turbidity in water.

Carbon prefilter phase

The carbon filter is designed to remove chlorine and other contaminants that affect the performance and life of the RO membrane as well as improve the taste and odor of your water. Change the carbon filter every 6-12 months. This will help to ensure membrane life and quality.

Reverse Osmosis membrane phase

The semi-permeable RO membrane in your RO system is designed to allow water through but filter out almost all additional contaminants. Change the reverse osmosis membrane every 24 months.

Polishing filter phase

In a four-stage RO System, a final post filter (carbon filter) will “polish” off the water to remove any remaining taste and odor in the water. Change this filter every 12 months to ensure quality water. Do not wait until taste is a problem.

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