How Do I Sanitize My Reverse Osmosis System? IN DETAIL!

I receive calls all the time from people who have just moved into a new home that has a reverse osmosis drinking water system.

They tell me that they are happy to have the system, but don’t want to use it because they don’t know what may be growing inside of the system. I tell them to change the reverse osmosis filters and sanitize the system, then they ask the inevitable question. How Do I Sanitize My Reverse Osmosis System?

You can sanitize a reverse osmosis system by adding a disinfectant to the system at its earliest filter stage with the filters and membrane removed from their housings, running the disinfectant through the system, and then flushing out the disinfectant after it has sanitized the inside of the system.

Although a reverse osmosis drinking water system is an enclosed water system that should not be exposed to air which can provide oxygen for bacteria to grow, tiny air bubbles in your water can often remain inside your system and lead to bacteria growth.

Sanitizing the interior surfaces of your reverse osmosis drinking water system when you change the filters of your system will help to stop bacteria from forming and provide healthier water for you and your family.

Things to know before sanitizing your reverse osmosis system.

For sanitizing your reverse osmosis drinking water system, I recommend using an EPA & NSF approved non-bleach sanitizer or about 3 tablespoons of simple un-scented household bleach.

Very important! When sanitizing ANY reverse osmosis drinking water system, it is very important that the membrane is removed from the system.

If a reverse osmosis membrane is exposed to chlorine bleach or any corrosive additive, it may cause the membrane to develop holes in the semi-permeable membrane material.

If holes develop in the membrane, the contaminants in the untreated water can channel their way through these holes and end up in your drinking water.

Things you will need for sanitizing your reverse osmosis system:

1: A new set of filters for your reverse osmosis system, including any specialty filters like a re-mineralization cartridge or UV bulb if your system has an ultraviolet light purification stage.

2: A clean towel (or two). We will be removing water filters from a water filtering system after all, so there is going to be some water to clean up as we go and afterward. Paper towels will work fine also.

3: Sanitized disposable gloves (like these) for handling the filters and membrane.

4: A small clean bucket is often handy for holding the filters or filter housings in so they don’t lay on the ground or spillover if they are full of water.

5: A clean work area and a flashlight so you can properly access and see what you are doing. I like to use this hands-free light that goes right on your head so you can see everything and leave your hands free.

6: Your reverse osmosis filter housing wrench. If you are unfamiliar with this wrench, it looks like a giant magnifying glass that Sherlock Holmes would use. It goes over the outside of the filter housings so you can loosen and remove them.

7: And of course an EPA & NSF approved non-bleach sanitizer.

If you are going to do any work on your reverse osmosis drinking water system, check out my article on What I Use When I Work On A Reverse Osmosis System!

Note: You should NOT use the filter housing wrench for tightening the filter housings when putting them back on. Only tighten the housings’ hand tight.

If the housing leaks after replacing it and it will not stop when you tighten it by hand, you can use the wrench to snug the housing slightly to get the leak to stop.

But first, check out my article on How To Fix A Leaking Water Filter. In Detail, With Images.

Steps to sanitizing a reverse osmosis drinking water system with standard housings:

Step 1: Wash your hands thoroughly!

Step 2: Shut off any ice makers or other water dispensers that use water from your reverse osmosis drinking water system.

Step 3: Turn of the water that is supplying your reverse osmosis.

This is usually a simple valve that is underneath the sink where your reverse osmosis is installed. It is often a white and blue or grey valve that turns on and off with a quarter turn, but it may also be a metal piercing valve that you need to close by turning it clockwise until it stops turning.

Step 4: Turn the reverse osmosis faucet on and let it run until the water stops completely. This will depressurize the system to allow you to work on it.

Step 5: Remove the pre-filter and post-filter housings. Many reverse osmosis systems will have these housings clearly labeled so you can not get them mixed up, but if yours are not clearly labeled, you can use a permanent marker or labels to mark the housings.

Also, put the filter information on the system itself so you will know which one goes where the next time you need to remove the housings.

Hint: Some people also like to write a description of what type of filter goes into each housing, write sediment filter 1 or carbon filter 3 on the housings.

You may want to even add the filter model number on the housing so you can easily see which filters you will need for your next filter change.

Step 6: With sanitary gloves on, remove the membrane, sediment filters and post-filters from there housings.

If you are just sanitizing your reverse osmosis and are going to be replacing the existing filters and membrane, be sure to place filters and membrane in a clean container or on a very clean towel or paper towels.

Step 7: Wipe the inside of the housings with a clean lint-free cloth or paper towels. If they seem very dirty, wash them out with mild dishwashing liquid and rinse thoroughly. Be careful not to dislodge the o ring that creates the seal between the filter housing and the system itself.

Step 8: Add non-bleach sanitizer or 3 tablespoons of non-scented household bleach to the first pre-filter housing of your reverse osmosis system, and replace the housing into its original position.

Do the same for the rest of the filter housings and membrane housing, leaving them empty for now. Only hand tighten the housings as we will be removing them again soon.

Step 9: Once you have replaced all of the housings to there original positions, turn the water supply valve back on and watch for water to start coming out of the system’s faucet.

Once you see the water begin to come out of the system’s faucet, shut off the faucet and let the system sit for 2-3 hours.

During this time, the non-bleach sanitizer or household bleach will be making contact with the internal surfaces of your reverse osmosis system and disinfecting them.

Since we added the sanitizer at the very beginning of the system and then turned the water on until the water came out of the system’s faucet, the sanitizer will make contact with all of the surfaces that would normally make contact with the water that you drink.

Step 10: Check for leaks on your system. While your reverse osmosis is being disinfected by the sanitizer is a great time to give your system a once over. Wipe the system down gently with a clean towel, checking for leaks or loose fittings as you go.

Do not attempt to fix any leaks or fittings at this point since the system is now under pressure, but make note of any leaks or fittings that you want to attend to after the disinfection process is complete.

Step 11: Flushing out the sanitizer. After you have let the sanitizer sit in your reverse osmosis system to sanitize it, turn on the system’s faucet and let the water run until it goes down to just a trickle.

At this point, you will have sanitized the inside of your reverse osmosis drinking water system, but some of the sanitizer may still be lingering inside of the system. Shut off the system’s faucet and let the system fill up again with fresh water for 2-3 hours.

After the system has filled for 2-3 hours, open the system’s faucet one more time and let the system empty again.

If you are not confident that all of the sanitizer has been flushed from your system, you can shut off the faucet and repeat the process until you feel that the system is free of the sanitizer.

Once the water has gone down to a trickle again, shut off the water supply to the system once more and wait until the water stops completely. This will depressurize the system again so we can re-install the filters and membrane or install the new filters and membrane.

Step 12: If you found any leaks while the system was being disinfected, now is the time to address them.

Leaks on a reverse osmosis drinking water system are usually caused by an o ring not sealing properly around a section of tubing or a cracked fitting.

You can replace leaking o rings by carefully pulling off the plastic grab rings that hold the tubing in place and removing the o ring that sits just under the grab ring.

I suggest replacing both o ring and grab ring as the o ring stops the leak, but the grab ring holds the tubing in place, so both are very important. Spread a thin layer of silicone-based o ring lubricant on the o ring to create a better seal between the o ring and the tubing.

Before reinserting the tubing into the o ring, be sure the end of the tubing is smooth and free of any sharp edges as they may cut a grove in the o ring when you re-insert the tube.

Step 13: Replacing the filters. Although I highly recommend putting new filters in at this point, if your existing filters are relatively new you may re-use them after the sanitization is complete.

Remove each housing one at a time and insert the appropriate filter into the housing.

I recommend leaving the water in the housing and holding the housing over the sink when inserting the new filters as this will help to minimize air bubbles getting trapped in or around the filters.

When inserting the reverse osmosis membrane and filters, be sure to be wearing sanitary gloves to avoid contamination.

Make sure that the o ring inside of the filter housing is free of any debris and screw housing back onto the reverse osmosis system. Continue replacing all of the filters and membrane and then dry the outside of the system thoroughly.

Step 14: Turn on the water supply to the reverse osmosis and watch for water to start coming out of the system’s faucet. Once you see the water flowing, shut off the faucet and allow the system storage tank to fill for 2-3 hours.

Now that your reverse osmosis drinking water system is producing filtered water, you should empty out the tank at least once before drinking from it to make sure that the water in the storage tank is properly filtered.

Step 15: Turn any ice makers or other water systems that use water from your reverse osmosis system and enjoy your reverse osmosis water as usual.

You may want to dispose of any old ice from your ice maker if you don’t believe that your reverse osmosis system has been working correctly, but if it has been fine, you should be able to just use the existing ice.

Additional stages to consider when sanitizing your reverse osmosis system.

Re-mineralization or Alkalinity cartridges:

If you are sanitizing your reverse osmosis drinking water system as part of your regular filter change, be sure to change any specialty filters or cartridges that are additional stages to your system.

Re-mineralization also sometimes referred to as re-alkalizing of reverse osmosis water is fast becoming a standard stage of many reverse osmosis systems. It usually involves the addition of a cartridge that contains calcite.

This calcite slowly dissolves and neutralizes the acid that is in the water. As it does this it also adds some flavor to the water which is often desired by coffee and tea lovers.

Although this cartridge is not actually a filter, it should be changed whenever you change the other filters of your reverse osmosis after the system has been sanitized.

Ultraviolet sanitization stage:

As the name of this stage implies, it is a stage where the water is passed through a cylinder that contains an ultraviolet light to sanitize the water.

When sanitizing your reverse osmosis system, I advise you to unplug this UV light so that it does not affect the rest of the sanitization process.

The ultraviolet bulb in this stage should be changed every time you change the other filters of your reverse osmosis because the intensity of the bulb diminishes over time and it will no longer be able to sanitize the water as intended.

How to sanitize your reverse osmosis storage tank.

If you have already followed the steps to sanitize your reverse osmosis drinking water system, you have already sanitized the storage of your system tank.

But if you would like to sanitize the storage tank in between sanitization of your whole system. Here is a simple way to do it.

Step 1: As in the complete sanitization process, we need to shut off the water supply to the reverse osmosis drinking water system.

Step 2: Turn on the reverse osmosis faucet until the water stops completely, this will depressurize the system and empty out the storage tank.

Step 3: Disconnect the tube going to the storage tank from the reverse osmosis leaving the tank end connected. This is usually done by pushing the tube into the connector, holding back the retention ring and then pulling the tube out of the fitting.

Step 4: Hold the disconnected end of the tube down at an angle and give it a few shakes to empty the water from it.

Step 5: Now hold the disconnected end up at an angle and put 3-5 drops of unscented household bleach down the end.

Step 6: Wipe off the disconnected end and re-insert it into the reverse osmosis system.

Step 7: Turn the supply water back on and watch for the water to begin to come out of the reverse osmosis faucet.

Step 8: Shut off the reverse osmosis faucet as soon as you see the water start to flow. Now you have added a sanitizer to the storage tank only, without affecting the entire reverse osmosis system.

Step 9: Allow the sanitizer to sit inside of the tank for about 1 hour. This will give the sanitizer enough time to sanitize the interior surfaces of the tank.

Step 10: After an hour has passed, turn on the reverse osmosis faucet and let the water flow until it reduces down to a trickle.

Step 11: Shut off the faucet and let the tank fill for 2-3 hours.

Step 12: Turn the faucet back on, and let the tank empty completely one more time to make sure no sanitizer is left over in the storage tank.

Step 13: Allow the storage tank to fill for 2-3 hours again.

Step 14: Enjoy your great-tasting reverse osmosis water.

Sanitizing a Kinetico reverse osmosis drinking water system:

The overall process of sanitizing a Kinetico reverse osmosis drinking water station is the same as any other standard type reverse osmosis system.

The problem with a Kinetico reverse is that you can’t remove the reverse osmosis membrane from its housing which is very important to protect your systems membrane.

To get past this problem, we are going to use your old filters as dummy cartridges, or you should get an additional non-carbon pre-filter from your Kinetico dealer to use in place of your reverse osmosis membrane.

Note: If you are changing your Kinetico reverse osmosis membrane anyway, you can just leave the old one in place for the sanitizing procedure and then replace the membrane after the system has been sanitized.

Hint: It is easy to get the new Kinetico filters (or any other enclosed filters) and membrane confused with the old ones. I recommend using a permanent marker to write the date on the new filters and membrane before starting a filter change and sanitizing procedure.

Step 1: Shut off the water feeding your Kinetico reverse osmosis.

Step 2: Turn off the faucet until the water has stopped completely.

Step 3: Remove the prefilter (Yellow or Purple) from the back end of the system.

Step 4: Add about 10 drops of household chlorine bleach to the opening on top of the new yellow filter and pre-fill it by slowly adding water to it from the side opening of the top. This is the groove that goes around the middle opening on top.

Holding the filter at a 45-degree angle helps to fill it quicker and easier. Fill the filter from the side groove until you see the water come up from the center.

Install the new yellow filter into the pre-filter opening.

Note: If you have municipal water, you should be using a purple filter during normal operation, but a purple filter contains carbon which will remove the chlorine bleach from the water.

You can get 2 yellow (non-carbon) filters for use only during the sanitization process. Be sure to put in a purple carbon filter in your pre-filter slot after sanitizing is complete.

Step 5: Remove the systems reverse osmosis membrane which is the one right in the center of the system and replace it with either the old yellow filter or a new yellow filter that you will use for sanitizing the system.

Fill this filter with water the same way as the pre-filter but no chlorine bleach is needed.

Step 6: Remove the systems post filter (Orange or Blue) and replace it with a filled yellow filter just as you did with the membrane.

If your system was still flowing well before you started the sanitizing process, remove the white (snowflake looking) piece from the top of the old post-filter, and put it in the top of the new yellow filter.

This will be your (dummy) cartridge whenever you want to sanitize your reverse osmosis system. Use a pair of needle-nose pliers to pull the piece right out and then just push it into the yellow filter.

Note: If you have any additional cartridges on a Kinetico K5 system, they should be replaced the same way as the pre or post-filters.

Step 7: Once you have replaced all three filters as instructed, turn the system’s water back on and allow the chlorinated water from the pre-filter to run through the entire system until you can smell the chlorine coming from the system’s faucet.

As soon as you smell the chlorine bleach, shut off the system faucet and allow the system to sit for 1 hour. After an hour, turn the faucet back on and allow the water to flow for 5 minutes to remove all of the chlorine bleach from the system.

Step 8: Shut off the water feed to the system once again, and wait for the water to stop.

Step 9: If you used a yellow pre-filter for the sanitization process but normally use a purple pre-filter for municipal water, pre-fill the new purple filter and put it in the pre-filter slot where the yellow sanitizing filter was.

If you are on a private well, simply leave the yellow filter that you added the chlorine bleach to in the pre-filter slot and proceed to the next step.

Step 10: Remove the yellow filter from the center slot where the membrane should be and replace the membrane from before.

If you are replacing your systems membrane because it is no longer filtering as needed, prefill the new membrane the same way as you did the yellow filters.

Step 11: Remove the yellow (dummy) cartridge from the post-filter slot and replace it with the water-filled new post filter.

Step 12: Replace any additional filters in the same way as you replaced the pre and post-filters.

Empty the old filters that you plan on using for the next time by standing them upside-down until empty and let them dry thoroughly. Store them in a clean plastic bag for use in the future.

Step 13: Turn the system’s water back on and allow the system to fill for 3 hours.

Step 14: Turn on the system’s faucet and allow the storage tank to completely empty, then allow the storage tank to fill with new filtered water for about 3 hours.

Step 15: Resume enjoying your reverse osmosis drinking water system

When should you sanitize a reverse osmosis drinking water system?

Since sanitizing your reverse osmosis is very beneficial and also not all that difficult to do, I highly recommend that you should sanitize your reverse osmosis system every time you change your reverse osmosis filters.

As a rule of thumb, I recommend changing your reverse osmosis filters once per year. But if you are only using a small amount of reverse osmosis water per day, changing your filters every 18 to 24 months may be adequate for your reverse osmosis system.

If you are very diligent about changing your filters every 18 to 24 months and you are using water from your reverse osmosis drinking water system on a daily basis, sanitizing your system every 18 to 24 months would be fine.

If you only use your reverse osmosis drinking water system on a part-time basis, like in a summer home or when the kids are home from college, you should consider sanitizing your system yearly even if you do not intend to change the filters.

If you have a large family that uses a large quantity of reverse osmosis water, you may find that you are changing your reverse osmosis filters more often than once per year.

If you are using large amounts of reverse osmosis water, the water inside of the system will tend to stay fresher and reduce the chance of any bacteria growth within the system. If this is the case, sanitizing your system yearly would be adequate.

Don’t forget to sanitize the reverse osmosis faucet!

Your reverse osmosis drinking water systems faucet is exposed to the open air, and therefore it is exposed to germs and bacteria growth. When sanitizing your reverse osmosis system, be sure to clean the faucet opening.

This is the contact point where bacteria can start growing, so sanitizing it is just as important (if not more important) as sanitizing the rest of the system.

Start by cleaning the end of the faucet with a little dishwashing liquid and water to remove as much of the external build-up as possible.

Next, take a little bit of unscented household bleach on a pipe cleaner or a clean paper towel that you have twisted to a point, and run it down the faucet opening as far as it can go. Twist and turn it in all directions to get the bleach everywhere you can inside of the faucet.

You can do this multiple times until you see the pipe cleaner or paper towel comes out clean. Run a pipe cleaner or paper towel down the faucet one last time with water only to remove extra bleach from the faucet.

When you are satisfied that you have clean out the inside of your faucet as best as you can, wipe the outside clean with some water, and run a few glasses worth of reverse osmosis water through the faucet before you start drinking from it.

Things to check while you are sanitizing your reverse osmosis system:

Check the fittings going in and out of the system for any leaks or cracks.

Leaking fittings are often just an o ring inside of the fitting that is not making a proper seal around the tubing that goes in the fitting.

Often, you can simply remove the o ring from the fitting and replace the o ring to solve a leaking problem. Put a thin layer of a silicone-based o ring lubricant on the new o ring to help it seal better, and to allow the tubing to slide into it easier.

If you have changed the o ring and the leak continues, the fitting may be cracked and need replacement. Most fittings on reverse osmosis drinking water systems use 1/4 inch and 3/8 inch fittings and tubing.

If your fitting does not appear to be one of these, be sure to get the advice of your local plumbing or hardware person to get the correct fitting or use a different fitting to replace your old fitting.

Check that there are no obstructions that may damage your reverse osmosis system.

Often, reverse osmosis drinking water systems are installed underneath the kitchen sink. This is often also the place where you store cleaning products and other kitchen products.

Since you are working in that area anyway, take a quick look around to make sure there is nothing that is too close to your reverse osmosis.

Move any objects that may hit tubing or fittings on your system, place larger objects in front of your reverse osmosis system to help to protect it from daily taking out and putting in of items stored next to the RO.

Make sure to dry the area thoroughly after working on your RO.

Drying the entire area very thoroughly is very important in preventing the growth of mold and mildew. Also, it is a great way to check for leaks or debris.