How to Sanitize a Reverse Osmosis System + Cleaning the Tank

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

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With time, the functionality of a reverse osmosis system might start declining, especially if the water quality is pretty bad. In such instances, cleaning or sanitizing the system helps remove scale and foul odors from the RO water, keeping it fresh as ever.

Additionally, it ensures that no microorganisms accumulate in the filter housings, the tubing, the water storage tank etc.

But like most homeowners, you might not know how to sanitize an RO system. That’s why we’ll discuss the steps in detail in this article so that you can save money that you’d otherwise spend on hiring a professional.

So, here is our step-by-step guide on how to sanitize a reverse osmosis system!


  1. Shut off the water source and relieve system pressure.
  2. Detach ALL the pre-filters and the RO membrane.
  3. Clean the housings by using a brush and dishwater or any appropriate sanitizer.
  4. Put bleach into the housing of filter stage 1.
  5. Put back all the empty housings and switch on the water source.
  6. Open the RO faucet and fill the storage tank. Let the bleach remain in the system for at least thirty minutes to a few hours.
  7. Flush all water. Refill the tank again and flush it out for a second or third time to ensure that all traces of bleach have been removed.
  8. Shut off the water source again and relieve system pressure.
  9. Insert the filter elements.
  10. Open the water supply and check for leaks.

How to Sanitize a Reverse Osmosis System?

How to Sanitize a Reverse Osmosis System Thumbnail

Before getting started with the explanation, let’s just remember that you don’t necessarily have to sanitize your RO system.

Only do it if you’re experiencing poor water quality despite the filters being new and functional.

Since the sanitization process is simple, it won’t take a lot of your time. Plus, it’s a good practice, especially if you have kids or sick individuals at home who cannot afford to drink contaminated water at any cost.

It’s ideal to clean a reverse osmosis water filter at least once a year unless you’re noticing scale and odors sooner. In that case, clean the system twice. The best time for this, in our opinion, is when you’re replacing the reverse osmosis membrane and the filter elements anyway.

Although some systems have specific instructions for sanitization, these steps are standard for most models:

  1. Wash your hands before you begin.
  2. Gather your supplies. You’ll need to fill a bucket with water and add a few drops of dishwashing liquid to make a cleansing solution. Also, keep a brush or scouring pad nearby. Finally, you need an NSF-approved sanitizer. Alternatively, you can use about three tablespoons of unscented bleach, chlorine or hydrogen peroxide.[1]
  3. Once you have all your supplies, turn the water supply off and discount refrigerators, ice makers or related electronic appliances.
  4. Turn on the RO faucet and keep it open till the flow stops. Doing so will release any pressure from the system.
  5. Then, remove the reverse osmosis membrane and the pre-filters from their designated housings. Make sure there’s no filter remaining in the system.
  6. Use the dishwashing soap and water mixture to clean the inner side of all the empty filter housings. Once all the visible dirt is removed, rinse the housings.
  7. Add bleach into the first filter housing.
  8. Screw the housings back in place, but this time without filter cartridges inside. At this point, only the post-filter should be installed in your system.
  9. Turn on the water supply and the RO faucet. Once the water comes out of the dispenser, turn it off.
  10. Allow the water storage tank to fill and let the mixture of water and bleach in the system for at least half an hour.
  11. Open the RO faucet to flush all water.
  12. Refill the tank again and flush a second time. If you cannot smell the sanitizer anymore, follow the next steps. Otherwise, flush again.
  13. Close the water supply and open the RO faucet to release pressure from the system.
  14. If you need to install a new RO membrane and pre/post-filters, do it now. If the old ones still have remaining capacity, install them back. Only the polishing filter hast o be replaced no matter what – it was exposed to the sanitizer.
  15. Open the water supply valve one final time and the RO faucet, too. Let the water run for some time and check if there are any leaks.
  16. Turn the faucet off and let the storage tank fill.
  17. Before you begin using the system again, make sure you flush out one to two tanks full of water. Check the instructions manual for any other guidelines.
  18. Now you can connect the system back to other appliances.

How to Clean the RO Membrane?

This section explains how to clean an RO membrane.

For this, you have to soak it in different cleaning solutions. In doing so, you’ll get rid of calcium precipitates, nasty particles, mold and organic matter, preventing foul smells, taste and scaling.

Here are the steps involved in this process:

  1. To protect yourself from the cleaning chemicals which can be quite aggressive, put on eyewear and gloves.
  2. Prepare the chemical solutions needed to clean the RO membrane as per the manufacturer’s instructions. Make sure the solutions are stored in non-reactive containers, or you’ll have to deal with a bigger mess.
  3. Turn off the water supply and the tank valve of your reverse osmosis water filtration system, letting it depressurize.
  4. Take the reverse osmosis membrane out of its housing.
  5. Soak it in each solution for the time recommended by the manufacturer. Rinse the membrane after taking it out of each solution.
  6. Assemble the system and flush it for about half an hour before using it again.

How to Clean the RO Tank?

If you’ve followed the steps for cleaning your RO system, you don’t have to clean the water storage tank separately. However, if you only intend on cleaning the RO tank due to foul smell or taste, follow the method given below.

  1. Close the water supply valve.
  2. Then, turn on the filtered water dispenser and let the system depressurize. Let it stay on until there’s no flow.
  3. Close the valve of the storage tank and remove its tube from the entire system. Let it stay attached to the storage tank, though. If there’s water in the tube, drain it.
  4. Put half a tablespoon of unscented bleach, hydrogen peroxide or chlorine in the tube using a funnel.
  5. Now, reconnect the tube to the system.
  6. Open the valve of the storage tank and keep the RO faucet turned off.
  7. Open the feed water valve.
  8. Allow the tank to fill. Let the bleach sit in there for half an hour to a few hours as it will kill pathogens inside.
  9. Turn on the RO faucet and let the tank drain. Refill it and flush out the water again. Do this unless there’s no smell of sanitizer in the water anymore.
  10. Finally, you’ll have to replace the post-filter unless it has been bypassed.


In conclusion, sanitizing a reverse osmosis system is one of the easier DIY tasks. But depending on your water quality, it’s necessary if you want to ensure that the functionality of your drinking water filter doesn’t get compromised. Also, sanitization prevents fouling and microbial infestation.

The best time for cleaning is when you’re replacing the different filter elements.

Wash your hands before you begin and then simply follow the instructions in your user manual. For reference, check our instructions above. Optionally, you can clean just the storage tank.

When cleaning the reverse osmosis membrane, you need to soak it in different chemical solutions.

All this shouldn’t take more than 1-2 hours total.

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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