How to Replace Reverse Osmosis Filters and the RO Membrane

Author: Rory Mullan - Published: 2021/07/08 - Updated: 2022/11/08

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Maintenance of a reverse osmosis system is imperative if you want it to live up to its potential.

After a certain period, pre-filters, post-filters and the reverse osmosis membrane lose their ability to filter contaminants out of water. Therefore, their timely replacement is important and allows you to enjoy nice-tasting, non-smelling and contaminant-free drinking water.

While it may sound a tad bit daunting, replacing these filter elements isn’t that difficult of a task. In fact, you can do it at home with a little help from our side.

So, here is our step-by-step guide on how to change reverse osmosis filter elements!


  1. It is important to sanitize your hands in order to ensure that you won’t contaminate the new filter elements.
  2. Shut off the water source and close the valve of the storage tank.
  3. Remove pressure from the system and drain any water from it by opening the reverse osmosis faucet.
  4. Detach the pre-filter housings. You can clean them with unscented household bleach, dishwater, or other appropriate sanitizers. Remember to thoroughly rinse them afterward.
  5. Put in place the new pre-filters and, if needed, change the post-filter.
  6. Open the housing and remove the old membrane. You can sanitize the housing if it is dirty. Remember to rinse it thoroughly.
  7. Install the replacement membrane. Make sure to push it until it clicks and is seated securely.
  8. Turn back on the water source, open both the RO tank valve and the RO faucet, and flush the system for a few minutes while you check for any leaks and misalignment.
  9. Lastly, you can close the faucet to allow the tank to fill, and then discard it. Do this 2 times.

Reverse Osmosis Filter Change

Besides knowing how to replace RO filters, you also need to know how often they should be changed.

How Often to Change Reverse Osmosis Filters?

Sure enough, you don’t want to replace the different filter stages of your reverse osmosis system more frequently than necessary since it’s costly. But you can’t delay the replacement for too long either since it becomes a health risk and filtered water quality diminishes.

The required frequency of replacement depends on these factors:

  • Water Quality: If there are high sediment levels in your drinking water or the water is too hard, it will lower the filters’ lifespan so that you’ll have to replace them more often. And these are only two examples of many possible water conditions you might be facing.
  • Water Consumption: Each water filter has a certain capacity, which refers to the number of gallons of water it can clean. If you use more water, you will be using up the filter’s capacity sooner.

As a general rule, a regular carbon pre-filter will last for six months to one year. The same applies to sediment pre-filters. On the other hand, a carbon post-filter can last for a year, while some are good for two years.

However, if you’re using low-quality filter elements, you will likely have to replace them more often. So, make sure you read the manufacturer’s instructions about filter replacement.

Sediment Pre-Filters

These filters are in the first and/or second stages of filtration in most RO systems.

They remove silt, debris, sand, and rust from the drinking water. Along with cleaning water, they also ensure no scratchy particles cause abrasion or clogging when they reach the reverse osmosis membrane.[1]

They also help prevent the inclusion of foul taste or smell in the water.

Carbon Pre-Filters

These filters are in the second (and third) stage of filtration.

They use some sort of activated carbon as a block or grains. Carbon pre-filters are effective in removing chlorine and other chemicals that can harm your health and damage the reverse osmosis membrane.

Carbon Post-Filters

These filters are present in the fourth or fifth stage of the filter process and remove any residual impurities in the water right before it comes out of the RO faucet.

Potential Issues When Failing to Replace on Time

If you do not replace your RO water filters at the right time, the following could occur:

  • Lowered purity of filtered water
  • Low water pressure and flow
  • Accumulation of waterborne pathogens, such as bacteria that can affect your health badly
  • A poor taste in water
  • A foul smell
  • An increase in water wastage raising your water bill

If you’re noticing any of these symptoms, it’s about time you replace the filters.

How to Replace RO Filters?

How to Replace Reverse Osmosis Filters Thumbnail

The pre-filters come before the reverse osmosis membrane in an RO system. They’re either sediment filters or have a carbon element that removes chlorine taste and odor among other impurities. One or more post-filters come after said membrane. Over time, these filters get saturated and need to be replaced.

The good news is you can do this yourself without hiring a professional. Before you follow our steps, make sure you read the manufacturer’s instructions, as they will give you specific information for your RO system model.

  1. Since you want to keep the new filters contaminant-free, wash your hands beforehand.
  2. Then, turn the water supply off and close the valve of the storage tank.
  3. Now, turn on the reverse osmosis faucet as it will help depressurize the system. Let any residual water drain away and close the faucet when there’s no more dripping.
  4. Turn the filters’ housings clockwise to remove them from the system. If a housing is too tight, you may need to use a filter wrench for the job. Since the filters have been cleaning water, they will still have some residual in it, so make sure you have a towel in case of a spill.
  5. Use a mixture of dish soap and water to clean the inside of the housings. Alternatively, you can use a sanitizer or unscented household bleach. Make sure you rinse all components properly after adding the sanitizer and dish soap solution.
  6. Now, insert the new pre-filters into the housings. Make sure the O-rings are tight in place since it helps prevent leaks. If needed, lubricate them with grease. After adding the new filter elements, tighten their housings using the wrench but don’t overtighten them.
  7. When replacing the post-filter, remove the old cartridge from the quick connect fittings.
  8. Then, add the new post-filter by pushing the tubing inside the fittings. Pull back gently to ensure the connection is secure.
  9. Now, turn on the water supply and open the storage tank’s valve.
  10. Turn on the RO faucet. While the system is flushing, look for leaks.
  11. Turn the faucet off and allow the tank to fill.
  12. Once the tank has filled to the top, open the RO faucet once more. Initially, you might see dark-colored water coming from the faucet, but that’s nothing to be concerned about. Let the tank flush once or twice before using the water.

How to Replace Modular System Filters?

When it comes to replacing modular system filters, the process is quite simple. You don’t have to depressurize the system or turn the feed water off.

Instead, just keep a bowl or bucket under the RO system and twist the old filters to disassemble them.

Then, replace them with new filters. Finally, just check for leaks, and you’re good to go.

Replacing the RO Membrane

It goes without saying that the reverse osmosis membrane is the most integral part of any RO system. It traps everything from heavy metals to bacteria. In order to keep the membrane working perfectly, you need to clean it regularly.

But you can only clean it so many times. After that, there’s a need to replace the RO membrane. Here’s how to do it:

When to Replace the RO Membrane?

If water pressure or flow reduces, that’s a sign that the reverse osmosis membrane or one or more of the other filter stages needs replacement.

A more insightful way of determining the current state of your RO membrane is using a TDS meter to test the rejection rate of total dissolved solids.

Start by testing the TDS in the feed water and then compare it with the level in the filtered water.[2]

Calculate the TDS rejection rate using this formula:

TDS in unfiltered tap water – TDS in filtered water / TDS of unfiltered tap water x 100

When the rejection rate goes below 80%, you need to replace the RO membrane.

How to Change the RO Membrane?

  1. First and foremost, wash your hands.
  2. Turn the water supply off and shut off the valve of the storage tank.
  3. Turn on the water dispenser as it will release the pressure in the system. Drain all residual water and turn off the faucet when the dripping stops.
  4. Then, detach the tubing from the housing cap of the membrane. In some models, there may be an additional plastic clip that you need to remove.
  5. Turn the cap clockwise to remove it.
  6. Remove the old membrane.
  7. Clean the inner side of the housing using a dish soap and water solution. You can also use bleach or a sanitizer but make sure to rinse the housing after adding these chemicals.
  8. Install the new membrane by pushing it into the housing. Insert it from the side that has two O-rings. Try not to touch the membrane while you’re installing it in order to avoid contamination.
  9. Make sure the O-rings are tight in place, and then put the housing cap back in place. If needed, you can also lubricate the O-rings using grease. If you can’t hand-tighten it, use a wrench.
  10. Now, push the water line inside the cap fitting for reconnecting the membrane.
  11. Turn on the water supply and the tank valve.
  12. Turn on the RO faucet and allow the system to flush for a few minutes. Look for any leaks in this duration.
  13. Turn the faucet off, letting the storage tank fill.
  14. Flush away one to two tanks of water as it will help remove any sanitizer or bleach leftover in the water. Once the smell is gone, you can start using the RO system again.

What is the Lifespan of an RO Membrane?

An RO membrane lasts for 3 to 5 years if you change the other filter stages at their designated times. However, if your water is extremely contaminated as is often the case with well water, you may have to change the membrane every other year or even once a year.


In conclusion, replacing the filters and membrane of a reverse osmosis system isn’t overly difficult.

Depending on your water conditions, pre-filters usually last between 6 months to 1 year. Post-filters can last 1-2 years. Semi-permeable RO membranes have a service life of 2-5 years (measure and calculate TDS rejection).

For replacement, wash your hands before you go to work and follow the instructions in your user manual. For reference, check our instructions above.

Not replacing the different filter stages according to schedule may pose a health risk. Drinking water quality can be compromised due to insufficient contaminant removal and microbial growth. This, in turn, can lead to bad water taste and odor, a drop in water pressure, and increased wastewater production.

Further Reading


Meet Rory Mullan

Rory Mullan Rory has joined the Water Masterz team as a contributing writer. He has covered all sorts of topics in the last several years.

Outside of his writing work, Rory enjoys photographing the Irish landscape and making music!

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