Reverse osmosis systems send water through a series of filters, which have a combined capability of removing more than 99.9% of all total dissolved solids (TDS).
These filters are incredibly effective at what they do, but, like most things, they don’t last forever.
If you want to continue to get the best out of your reverse osmosis system, you need to change your filters as recommended by your system’s manufacturer.
In this guide, I’ll discuss how often you should change each filter in your RO system. This is based on the requirements of RO systems on the whole, but be sure to check your user manual for confirmation.
How Often Should You Change Reverse Osmosis Filters?
|Sediment Filter||6 - 12 months|
|Carbon Filter||6 - 9 months|
|RO Membrane||2 years|
|Polishing Filter||6 - 12 months|
*Note that filter replacement schedule will vary depending on usage and local water conditions
The first filter stage of a reverse osmosis system is the sediment pre-filter. This filter has a slightly bigger larger size and removes suspended contaminants like sand, dirt, dust and rust, preventing them from clogging up and damaging the later-stage filters.
Typically, the sediment pre-filter requires replacing once every 6 months to 1 year.
A carbon filter usually has a lifespan of 6 to 9 months, after which it will require replacing.
At the heart of all reverse osmosis systems is the reverse osmosis membrane. This is the most important filter in the entire system, and is responsible for removing the majority of impurities, both dissolved and surface contaminants, from water.
You need to replace the reverse osmosis membrane after an average of 2 years, with some lasting up to 4 years.
Carbon Post/ Polishing Filter
Finally, the carbon post-filter removes any lingering contaminants that may have been small enough to pass through the RO membrane.
The post-filter may also remove any contaminants that may have leached into water while it was sitting in the storage tank.
Because the post-filter comes into contact with fewer contaminants, it usually lasts longer than a pre-filter, and you’ll only need to think about buying a filter replacement after every 6 months to 1 year.
That said, it’s important that your post-filter still gets changed when it needs to be, especially if your system has a water storage tank.
How to Change Filters in a Reverse Osmosis System
The exact filter change process in a reverse osmosis system may vary from manufacturer to manufacturer, but most systems are designed to make it as simple as possible.
❗️ Before beginning, I highly recommend checking your system’s manual. It will include detailed instructions about any specifics for changing the membrane on your unit.
How to Replace Carbon & Sediment Filters
To replace the carbon and sediment reverse osmosis filters in your system, follow the below steps:
Step 1: Purchase the correct filters for the replacement.
I would recommend buying directly from the brand, or from the brand’s Amazon page, for peace of mind. You may be able to purchase non-branded products that fit in your particular system, but this can be risky, so make sure to thoroughly read customer reviews before parting with your cash.
Step 2: Wash your hands
Clean with soap and water before getting started, which will prevent germs on your skin from contaminating the filters.
Step 3: Turn off your water supply
This will prevent water from passing into the system. If you have a storage tank, close the ball valve. Additionally, if your system is connected to your ice maker or refrigerator, close off access to this valve, too.
Step 4: Drain the waterline
Switch on your dedicated RO faucet and wait for any lingering water to empty out of the system. In preparation for potential leaks, place a bucket or a tray underneath the filter housing, which will catch any drips.
Step 5: Remove old filters
Unscrew the filters that need changing from the filter housing and dispose of them sensibly (many reverse osmosis filters can now be recycled, so check with your manufacturer if you’re unsure). You can use the wrench provided by your manufacturer if the filters are a little stiff.
Step 6: Remove & clean O-rings
Remove the filter housing and the system’s O-rings, wipe them with a cloth and place them on a clean surface. You can use this time to check over the O-rings and make sure they’re still in good condition.
Step 7: Clean filter housing
Clean the inside of the filter housing with a little soap and water. Dry thoroughly and ensure that all soap is removed, then reattach the housing to your unit.
Step 8: Lubricate the O-rings
Properly lubricate then insert them back in the space you removed them from. Make sure the O-rings are correctly positioned to prevent leaking.
Step 9: Insert new filters
Unwrap your filter replacement from its plastic packaging, then insert the filter replacement into the housing and screw it in place. You can hand-tighten or use the provided filter wrench, but you shouldn’t force the filters too tightly.
Step 10: Turn on the water
Turn your water supply back on and check that there are no leaks. If leaks are detected, tighten the RO filters a little more or check that your O-rings are properly positioned.
Step 11: Flush & test
Switch on your faucet and wait for the water to flow through, which indicates that your filters are correctly installed and your system is ready to use again. If your system has a storage tank, don’t allow water to pass into it just yet.
Step 12: Fill storage tank (if applicable)
After you’ve allowed water to flow from your faucet for 5 minutes, switch off the faucet and open the ball valve connecting to the storage tank. Wait for your storage tank to fill, then open the valve connecting to your refrigerator or icemaker, if applicable.
Your reverse osmosis water filtration unit should be ready to use once more.
How to Replace the Reverse Osmosis Membrane
If you’re just replacing your RO membrane, the process is slightly different:
Step 1: Clean & prep
Follow steps 1-4 above, switching off your water supply and washing your hands before getting started.
Step 2: Disconnect tubing
Look on the right side of your filter housing for the tubing that connects to the membrane housing cap. Disconnect this tubing, pressing down on the small ring around the tubing as you do so.
Step 3: Remove old membrane
Unscrew the cap off the top of the RO membrane housing and ease the membrane out of the housing. You might have to use additional tools to remove the membrane if it’s wedged inside the housing.
Step 4: Clean membrane housing
I would advise taking a little extra time to clean the membrane housing, considering you probably won’t have cleaned it for at least 2 years. To do this, disconnect the tubes at the other end of the membrane cap. If it helps you to remember, color-code or label the tubes so you know where to insert them when you’re done.
Wash the inside of the membrane housing in a bowl of warm, soapy water, then rinse thoroughly under your faucet. Dry the membrane housing completely before reattaching it to your RO system.
Step 5: Insert new membrane
Remove the packaging from your replacement membrane and push it into the housing, checking that the end with the O-ring goes in first. Keep pushing until you feel the O-ring make contact with the base of the housing. You should use some force here to ensure that the membrane is properly in place.
Step 6: Replace membrane housing cap & tubing
You can now screw the cap back onto the membrane housing and connect any of the tubing you removed earlier. It’s important to push the tubing into the fitting until it won’t go any further, which will ensure it’s properly secured and prevent leaks. Give the tubing a quick pull once you’ve done this to lock it in place.
Step 7. Flush, test & run the system
Follow steps 10-12 above to complete your installation and get your reverse osmosis water filtration system up and running again.
Frequently Asked Questions
How do I know if my reverse osmosis filter is bad?
The easiest way to know when to change the filters in your reverse osmosis system is to simply note it down. When you install your filters, mark your calendar when they will have to be replaced. Keep in mind that your sediment filter, carbon filter and post-filter all have slightly different lifespans.
Of course, we’re not all organized enough to write down exactly when our filters require changing. If you’re going off guesswork alone, there are three signs to look for that suggest your reverse osmosis filter has gone bad:
1. Low water pressure
Reverse osmosis systems are usually capable of providing you with clean water almost instantly. If you’re getting impatient waiting for your glass of water to fill, it might be a sign that your reverse osmosis filter cartridges need changing. That’s because a clogged, older water filter is going to take so much longer to do its job than an unclogged filter.
2. Bad taste
If your water starts to taste unpleasant, it’s probably a sign that you need to install some replacement filters in your RO system. If you’re in need of a carbon filter change, you might taste chlorine in particular in your water.
3. Poor efficiency
Finally, your RO system may not work as efficiently if the water filter cartridges require changing. Listen out for the sound of your system running. If it seems to be constantly in operation, it’s a sign that it’s doing its job slower, and for longer.
Are all reverse osmosis filters the same?
No – and I mean that in the sense of replacing a water filter in a reverse osmosis system. Most systems have different sized filter housing, so one reverse osmosis filter cartridge is unlikely to fit in a system produced by a different manufacturer.
Some reverse osmosis water filters also have a larger number of filters, and will therefore require more filter changes.
Additionally, how often you have to replace your water filters may be affected by the quality of the product, which is why it’s always advisable to spend a little more upfront on a product from a water treatment manufacturer you can trust.
How do I know if my RO membrane needs replacing?
If your RO system needs a new membrane, you’ll probably notice similar signs to if your system needed a filter replacement.
Typically, two things will happen when a new membrane is needed: the system will become less effective at removing impurities, and the output of filtered water might drop. Both of these are undesirable, considering it means you’ll end up drinking unfiltered water and dealing with more water waste.
Over your months of using this form of water treatment, you’ll come to understand how your RO water filter usually operates. If your water quality decreases, the flow of water drops, or the system is working harder, for longer, these are all signs that it’s time to get your RO membrane replaced.
What affects the lifespan of RO water filters?
There are a few things that may affect how often your RO filters need to be replaced. Your daily water usage is a big one. Manufacturers can only guess how many months a filter might last based on average water use, but if you have a large family, your filters may become clogged more quickly.
Another thing that may affect your RO filter lifespans is your water quality. The more impurities your water contains, the harder your system will have to work, and the faster the filters will clog. If you live in an area with particularly contaminated water, trust your instincts and replace the filters more frequently if necessary.
How much do replacement RO filter cartridges cost?
The cost of a filter replacement usually depends on the brand or manufacturer you’re buying from. You can usually buy a pack of all the filters you need for a single system for $60-$100, while RO membranes on their own can cost anything from $30 to $75. This is a pretty small investment, considering you only need to pay for new filters after 6 months, minimum.