A well-maintained reverse osmosis filter will improve your drinking water quality for years to come. But replacing the filters is a little more challenging than changing the carbon cartridges in filtration pitchers.
Still, it’s a simple process that requires no plumbing skills or technical expertise. All it takes is your patience and our know-how.
Let’s review how to replace the filters in a reverse osmosis system.
Why Is It Important to Maintain Reverse Osmosis Water Filters?
Reverse osmosis systems rely on a series of filters to purify your water. If any one of them isn’t functioning properly, the entire RO system and your water quality will suffer.
Carbon pre-filters, for example, remove contaminants that are hard on the reverse osmosis membrane. So, regular maintenance is the key to enjoying good water quality and extending the life of your water filtration system.
How Often Should You Change Reverse Osmosis Filters?
The average reverse osmosis system has four filters with lifespans that vary depending on feed water quality and usage:
Made of wound string or fibrous paper, sediment filters trap large particles of dirt, sand, rust that can clog the RO membrane. How long they last depends on how dirty your water supply is, but 6-9 months is average.
Carbon pre-filters remove contaminants that make your water smell and taste bad. Some, like chlorine and iron, can seriously shorten RO membrane life.
Like a sediment filter, how often a carbon filter should be changed depends on your water contaminants and usage — the more water you use, the harder they work. Most last 6-9 months.
The Reverse Osmosis Membrane
RO membranes do the heavy lifting in a reverse osmosis system, removing 99-percent or more of total dissolved solids, heavy metals and more. Under optimal conditions, they last 3-5 years.
The purpose of a post-filter is to remove trace substances that the carbon and RO filter missed. Called polishing filters, they refine water’s taste.
Light-duty, a carbon post-filter lasts longer than a pre-filter — up to 24 months. Most homeowners change it when filtered water starts to have an off-flavor.
Step-by-Step — How to Change a Reverse Osmosis Membrane
All reverse osmosis filters are different, so always refer to the instructions in the owner’s manual for how to change reverse osmosis membranes. But here’s the general procedure:
If you have the tools and supplies you’ll need handy, you can wrap up an RO membrane change in less than a half-hour.
- The filter wrench that came with your system
- Needle-nose pliers
- Paper towels
- An empty bucket to hold the old membrane
- A pail of soapy water
- A marker
- The new membrane
- Replacement sediment and carbon filters — why not do a complete filter replacement while you change the RO membrane?
#1 Wash Your Hands
Dirt, skin oil, and chemical residue on your hands can damage the new membrane. Wash your hands thoroughly with soap and warm water before you start the installation process.
#2 Turn Off the Water Supply
Turn off the water supply valve under the kitchen sink and close the storage tank valve.
#3 Depressurize the System
Next, depressurize the system by opening the reverse osmosis faucet. Let it run until any remaining water has been purged from the system. Lingering water may drip, so have a paper towel ready.
#4 Remove the Used Membrane
Remove the water supply line from the filter housing cap by pushing the collet against the fitting. Then take off the cap and remove the old membrane, prying it out of the membrane housing with pliers if necessary. Drop the old filter in your dry bucket.
#5 Clean the RO Membrane Housing
Sanitize the inside of the RO filter housing and the membrane housing cap, including the O-ring and threaded fittings, with warm soapy water and bleach if recommended by the manufacturer. Rinse them thoroughly to remove all residue so that the new membrane has a clean surface to cling to.
#6 Install a Fresh Membrane
Push the new membrane in, O-rings first, until it’s firmly in place — avoid touching it with your bare hands. Reassemble the filter housing and reconnect the water supply tubing by pushing it into the cap, pulling back on it lightly to ensure it’s properly secured.
#7 Turn On The Water
Restore feed water to the system and open the ball valve on the water storage tank. Next, turn on the RO faucet and flush the system while checking the filter housing and membrane housing cap for leaks. If you see a drip from the membrane housing, remove the check the O-ring — it’s the most common cause of filter leaks.
#8 Repressurize the Filter System
Close the RO faucet and let the storage tank refill. Discard the first tankful to flush out any dust or chemical preservatives on the membrane. Jot the filter replacement date down on the housing cap, so you remember when it was last changed.
You are now ready to use your reverse osmosis system.
When It’s Time to Replace Reverse Osmosis Filters?
The RO membrane is the most expensive filter in a reverse osmosis system, so you don’t want to replace it if it’s not necessary. But how can you tell when it’s time to change filters?
Here are your options.
You can change filter cartridges on a schedule, replacing old filters with new filters at specific intervals. Easy to remember, it’s better than falling behind on maintenance, but you run the risk of changing filters too often. With as many filters as there are in a reverse osmosis filter, that costs money.
But by then, hazardous substances could be in your drinking water and the membrane could be damaged. Overall, that’s neither a safe nor a cost-effective solution. Instead, we recommend testing your water monthly with a TDS meter.
TDS meters measure the total dissolved solids in water by measuring their electrical charge. And like a water softener, a reverse osmosis water filter removes nearly all dissolved solids, so a rising TDS concentration suggests the membrane is no longer filtering efficiently. For less than $40, a TDS meter is an indispensable tool.
What Does It Cost to Change Reverse Osmosis Filters?
The long-term cost of owning a reverse osmosis water filter is a bargain for the filtration quality it provides. Dollar for dollar, an RO system removes more contaminants than most other filters combined.
The upfront cost is low with quality RO filters starting at just $200, and maintenance is affordable. You’ll rarely have to replace all the filters at once, so you can budget for it.
The costliest filter replacement in RO systems is the membrane at $50-$75. There was a time when a new filter would set you back $150 or more, but prices have come down as the technology goes mainstream. Assuming the filters at each filter stage perform as expected, periodic maintenance for an RO system should cost less than $150 annually.
Saving on Reverse Osmosis Replacement Filters
These tips will help lower the cost of maintaining your reverse osmosis system:
Buy Filters in Bulk
A single sediment filter cartridge can cost up to $30. But by buying in bulk, you can reduce the new filter price by half. Why pay more for replacement filters than you have to?
Replace Filters Regularly
You have to spend money to save money when it comes to a reverse osmosis filter. Skimping on a cheap carbon filter cartridges can damage a costly membrane, so change the water filters before they get clogged. Post-filter replacement isn’t as critical for the service life of your system.
Maintain the Entire System
Reverse osmosis systems have dozens of components that all affect how the filter works, so maintenance is more than just filter replacement. A faulty O-ring or cracked filter housing, for example, can spoil a new filter.
Checking these parts and replacing them as needed — O-rings cost pennies — will reduce maintenance mishaps. With proper care, water filters can last decades. If you need a new reverse osmosis system – have a look a these top rated systems.
Reverse osmosis filters require occasional TLC, but like any investment, if you take good care of a water filter, it will take good care of you. We recommend keeping this guide and replacement filters on hand, so you’ll always be maintenance-ready.