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How To Sanitize a Reverse Osmosis System: Our DIY Guide

Sanitize RO system

Sanitize your RO system at least once a year.

This gets rid of any bacteria and other microbes that may have contaminated the filter cartridges and housings, the tubings and other internal components of the system.

If you do not regularly sanitize your RO system, these microbes can also contaminate your drinking water.

To make sure you don’t forget to sanitize your reverse osmosis system, we recommend doing it on the day you replace your filters. Most RO systems need filter replacements once a year.

What You’ll Need

In-line carbon post filter
  • New filter cartridges if you are also replacing the filters.
  • A new in-line post-filter.
  • 5% unscented bleach or the manufacturer-recommended sanitizer.
  • Filter housing wrench (not necessary if you can remove filter housings by hand).

Step-by-Step RO Sanitizing Process

Some important tips before you start.

Make sure the area around the RO system is clean to avoiding introducing dirt or dust into the filters.

Also, if you are replacing the filters, leave the new filter cartridges in their packaging until you are ready to install them. This ensures they do not get contaminated.

Check that you have everything you need with you and then follow the following steps to sanitize your RO system.

Note: These are just general directions. Check the maintenance part of your system’s user manual for specific sanitizing directions. If there aren’t any, the following steps apply to most under-sink RO systems.

  1. Wash your hands with soap and water. You can also put on a pair of sanitary gloves to prevent contamination and protect your skin from the bleach.
  2. Turn off the cold water supply to the RO system. If you also have a connection to the icemaker or fridge, turn that off too.
  3. De-pressurize and drain the RO system by turning on the RO faucet. Leave it on until the water stops running and then turn it off. Now you can open up the system.
  4. Using your hands or a filter housing wrench, unscrew the pre-filter housings and remove the used filter cartridges. Be careful not to tip the filter housing as it may still contain some water. Discard the used filter cartridge.
  5. Remove the RO membrane. If you are replacing the membrane, discard the old one. If not, put the old membrane in a plastic bag and place it somewhere clean. Make sure your hands are clean or you have sanitary gloves on before handling the RO membrane.
  6. Do not remove the in-line post-filter.
  7. Rinse the empty filter housings with mild soap and warm water. Be careful not to lose the O-ring at the top of the housing.
  8. Add 2-3 tablespoons (or whatever amount the manual recommends) of unscented bleach to the first pre-filter housing and screw it back onto the filter head. Re-connect the other pre-filters as well without any cartridges inside. Close the membrane housing cap.
  9. Turn on the cold water supply to the RO system and check for any leaks. Give the system 5-10 minutes to fill with water. The bleach solution will be carried from the first filter housing to all other components of the system.
  10. Open the RO faucet and wait for the water to start flowing out. This indicates the bleach solution has filled the system. Turn off the faucet and leave the system to soak in the solution for 1-2 hours or whatever time the manual recommends. Also, turn off the cold water supply to the RO system to prevent new water from entering the filters.
  11. Now it’s time to rinse the system, which will get rid of the smell and taste of bleach. Turn on the feed water valve and the RO faucet. Let the water run for around 5 minutes or until you can’t smell the bleach.
  12. Next, flush the system twice. Turn off the faucet and let the RO tank fill-up then open the faucet to drain it. Repeat this once more.
  13. With the system flushed, it’s time to put back the RO system together. Turn off the feed water valve and drain the system by turning the faucet on until it stops running. Then turn it off.
  14. Remove filter housings and put in the new filter cartridges. Put the membrane back into the membrane housing. Swap the post-filter for a new one. Make sure all connections are tight. If there’s a damaged O-ring on one of the housings, replace it to prevent leaks.
  15. Open the feed water valve and check for leaks. If everything looks good, follow the flush routine the manual outlines for new filters. This usually involves draining the first 2-3 tanks.
  16. Your reverse osmosis system is now sanitized.

To learn more about RO system maintenance, read out recent reverse osmosis system buying guide.

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