Reverse Osmosis Water Filter System Maintenance – Guide & Schedule

Author: Rory Mullan - Published: 2021/07/16 - Updated: 2022/11/08

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A reverse osmosis system is an incredibly powerful water filter that can remove a large number of harmful contaminants from city water and well water.

Since they are comparatively easy to maintain, robust systems are widely used around the world. Additionally, with proper maintenance, an RO system can serve you for a lifetime.

If you are a proud owner and worried about efficiently maintaining your system to increase its longevity, we’ve got you sorted.

So, here is a quick guide to help you maintain your reverse osmosis system!


  • The most important thing to remember is to change pre and post-filters regularly.
  • For pre-filters, they should be changed every six to twelve months. As for the post-filters, most of them last and should be replaced every one to two years.
  • Additionally, after you replace every filter, you should sanitize the whole system.
  • If the maintenance and replacement of pre and post-filters are properly observed, an RO membrane should serve you for two to three years.
  • At least once a year, use a low-pressure gauge to do a checkup on the storage tank pressure. Ideally, the pressure should be around six to eight psi when the tank is empty. If the pressure is not up to spec, you can use a bicycle pump to repressurize.

Reverse Osmosis System Maintenance Overview

How to Maintain a Reverse Osmosis System Thumbnail

A standard RO unit consists of three stages: Pre-filtration, reverse osmosis membrane and post-filtration. Pre and post-filtration often combine more than one filter element. Most reverse osmosis systems also include a storage tank.

With that said, here is a breakup of tasks and maintenance required by an RO system.

  • Replacing pre-filters: Every six to twelve months.
  • Replacing post-filters: Every one to two years
  • Replacing reverse osmosis membrane: Every two to three years
  • Sanitizing the unit: Every twelve months
  • Checking storage tank pressure: Every twelve months

RO System: When to Replace the Water Filters

For the RO membrane to work effectively, prompt replacement of pre-filters is highly essential. Changing post-filters on a regular basis provides for pristine water taste.

The most crucial aspect to consider when replacing filters is to get the manufacturer recommended replacements.

In case you find them too expensive, you can select cheaper options. Not to forget that a high-quality filter will improve system performance compared to a cheaply made poor-quality cartridge. Of course, you might also end up paying more in the long run due to more frequent replacements.

Replacement Frequencies

We mentioned above that pre-filters need to be replaced every 6 to 12 months, post-filters every 1 to 2 years. Now this timeline can vary for each household. Here is why:

  • Water quality in each household varies greatly. For example, those dealing with water from a private well will need more frequent replacements. This is because the pre-filters have to work extra hard to remove sediment and dirt.
    Moreover, some states have cleaner municipal water than others, so filter life may increase.
  • Secondly, water consumption differs for each household, too. A bigger family needs more water, and thus the filters will wear out quicker.

This brings us to the question of how to access filter performance. Here are four major indicators that highlight it’s time to replace:

  • If you see a decline in water quality over time, and the water doesn’t taste as clean as earlier, it’s the major red flag that filters are clogged.
  • Moreover, any unpleasant tastes or smells in the water signify the growth of microorganisms and bacteria in your filtration system. Proper sanitization can be essential in this case.
  • Similarly, if you feel the water pressure in your RO faucet has gone down and takes longer to fill a pitcher, a clogged filter is likely to blame.
  • Not to forget, a poor reverse osmosis filtration system will lead to major water wastage and less filtered water. Neither is this economical for you nor eco-friendly.

Sediment Pre-Filter

The first stage in most RO filter systems is a sediment filter. It traps dirt, debris, rust, little rocks or any other fine sediment down to 5 microns for example.

Depending on your water quality and water consumption, the average life of a sediment filter is 6 to 12 months. If you fail to replace the filter timely, the RO membrane will not work effectively either.

Average service life: 6 to 12 months

dirty filter cartridge

Carbon Pre-Filter

Next in line is the carbon block or granulated activated carbon (GAC) filter. This stage absorbs chlorine and other unwanted pollutants that affect the smell and taste of water.[1]

Again, this stage is an important stepping stone to purify water from unwanted chemicals etc. If this stage isn’t working efficiently, the RO membrane will fail to work due to exposure to chlorine.

Average service life: 6 to 12 months

Carbon Post-Filter

The last stage is a carbon filter that polishes your water, so it tastes clean, pure and natural. Since the post-filter is dealing with minimum contaminants, it lasts longer than a pre-filter.

Average service life: 1 to 2 years

How to Replace the Filters

Once you have acquired the appropriate filters for your RO unit, it’s time to begin replacement. Wash your hands thoroughly to avoid contaminating the filter cartridges.

All you need is a few basic supplies and a little time on your hand.

Tip: Remove filters one by one to avoid confusion during replacement.

  1. Close the shut-off valve and storage tank valve.
  2. Open the RO faucet to remove pressure from the system and let all the water flush out. Turn it off when no more water is dripping.
  3. Remember to keep a bucket handy to collect water spills when you open the filter housings.
  4. Unscrew the housings one at a time and replace the cartridges.
  5. Gently screw back the housings and tighten using a filter housing wrench (usually provided with the unit). Don’t overtighten, or you’ll end up breaking the housing or flattening the O-rings, causing leakage.
  6. Turn on the shut-off valve and storage tank valve.
  7. Turn on the RO water dispenser and let water flow out for a few minutes.
  8. Empty the tank and let it refill. Then flush the entire tank again before using the unit.

RO System: When to Replace the Membrane

As a rule of the thumb, RO membranes last up to 2 to 3 years. But if you feel your water quality has declined, a TDS check will help you figure out its performance. If your TDS meter shows a total rejection rate below 80%, it’s time for a replacement.

Keep in mind that if you have added a remineralization stage, TDS values will typically be higher.

Periodically sanitizing your RO membrane to remove mold and mildew is also recommended. It is advisable to use chemical solutions (depending on the model and manufacturer) to clean your RO membrane once a year.

RO Membrane Replacement Guide

A reverse osmosis membrane is the heart of any RO system. It is a semi-permeable thin film that separates the solvent from almost all the solutes.

Nevertheless, it’s not trickier to replace an RO membrane compared to the other filter elements. For extra safety, consult the manual for individual instructions and follow them to the dot. The procedure looks something like this:

  1. Wash your hands.
  2. Close water supply valve and storage tank valve.
  3. Drain all residual water.
  4. Unplug the tubing connected to the membrane housing.
  5. Unscrew the housing cap.
  6. Replace the RO membrane inside the housing. Try not to touch the new membrane.
  7. Put the housing cap back in place with the O-rings seated properly.
  8. Reconnect the tubing.
  9. Open water supply valve and storage tank valve.
  10. Turn on the RO faucet.
  11. Flush the system.
  12. Drain 1-2 full storage tanks.

RO System: Sanitizing the Tank

under sink reverse osmosis system with storage tank

Sanitizing your RO system is not necessary per se, but it is highly recommended by water professionals. If the water stays in one place too long, it becomes susceptible to unwanted bacteria, a health hazard.

The ideal time to deep clean and sanitize your entire unit is when you replace filters. This way, you kill two birds with one stone and can easily keep track of your maintenance schedule.

Here are the basic steps to follow.

  1. First, turn off the feed water supply to the unit.
  2. Next, drain the tank to depressurize the system.
  3. Then, remove all the filter housings and cartridges.
  4. Use warm soapy water and clean the housings properly. You can use household bleach[2] or an anti-bacterial cleaner to sanitize the housings.
  5. Now, fill the first housing with NSF-certified sanitizer or household bleach. Screw back all housings without the cartridges. Turn on the water supply and turn on the faucet to ensure all connections are secure.
  6. When you turn on the water supply, the feed water will transport the bleach to your storage tank.
  7. Let it sit for a few hours to properly sanitize the tank from inside.
  8. Finally, you can turn on the faucet and let all the water flow out. Ideally, you must flush the unit thrice to remove all traces of sanitizer/bleach from the tank.
  9. Now, you can replace all the filter elements securely and check the system for leaks.

Repressurizing the Tank

Maintaining the pressure of an RO tank is essential to prevent malfunctioning. Since RO tanks lose about 1 psi each year, periodic checks are essential.

Here is how to repressurize the tank.

  1. Make sure to measure the tank’s pressure when empty.
  2. You can use a simple tire gauge to measure the pressure of your RO tank. The pressure should range between 6-8 psi for a 2-4-gallon tank.
  3. If it’s less, use a bicycle pump or air compressor to increase pressure.

Professional Maintenance Service

Reverse osmosis systems will last you ages if maintained properly. But if you feel you’ll end up compromising the system, you can consult the manufacturer for after-sales service.


In conclusion, it’s important to maintain a reverse osmosis system for highest water quality and a long service life.

Pre-filter replacement is due every six to twelve months. Post-filters can last up to two years. An RO membrane can easily serve for 3 years.

Changing the different filter elements can be done within half an hour. The process is simple enough.

Other RO maintenance tasks include sanitizing the water storage tank and also checking its pressure. In case tank pressure is too low, repressurizing is required.

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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