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Sanitizing RO Systems

There are two basic types of residential reverse osmosis system.  

The traditional type with housings for the pre-filters and the membrane.  The filters are separate and placed in the housings.

The quick change type systems have encapsulated filters and membrane within a cartridge.  Filter changes require simple removal and replacement of individual cartridges, which have the filters within them.  They are essentially one piece systems where filters can not be removed from the cartridge.

For sanitizing quick change filter systems, with no filter housings, please follow these steps.

For these systems you have to sanitize only the tank and faucet.  Here’s how.  

This procedure should be done whenever it’s time to replace the post, carbon filter, usually once a year.  For reference, the pre-filters are normally changed every six months.

  • BEFORE YOU CHANGE THE POST CARBON FILTER, shut off the water supply to the system
  • Empty the tank by turning on the faucet and letting run until water stops
  • Check tank, by lifting it to see if there is still water in it.  Chances are, if you haven’t done maintenance in over a year, that it will still have water in it as it is low on air pressure
  • Use bike pump to increase pressure in tank through the air valve.  You will likely see more water coming out, from the faucet.  It only needs to be about 7 psi to get all the water out and function properly.  DO NOT OVER-PRESSURE THE TANK ABOVE 8 PSI
  • Once the correct pressure is established and all the water has been emptied, you have to remove the tank line at the connection to the system.  You may have to remove it at the tank as well to get all the water out of the line, then re-connect the line at the tank only
  • Take about 0.5 ml (about a teaspoon) of household bleach and inject it into the tank line, with a syringe, if possible
  • Reconnect the tank line to the system
  • Make sure the faucet is in off position and turn the water supply back on
  • Allow about 2 hours for the tank to refill and to sanitize
  • Turn on the faucet and empty the tank completely
  • Your system has now been sanitized
  • You can now change the post carbon filter, as well as the pre-filters.
  • Make sure you empty, at least, two tanks of water, before re-using water from the system

For sanitizing traditional reverse osmosis systems with filter housings, please follow the steps below.  This should be conducted once every year.

  • BEFORE YOU CHANGE THE POST CARBON FILTER(S), shut off the water supply to the system
  • Empty the tank by turning on the faucet and letting run until water stops
  • Check tank, by lifting it to see if there is still water in it.  Chances are, if you haven’t done maintenance in over a year, that it will still have water in it as it is low on air pressure
  • Use bike pump to increase pressure in tank through the air valve.  You will likely see more water coming out, from the faucet.  It only needs to be about 7 psi to get all the water out and function properly.  DO NOT OVER-PRESSURE THE TANK ABOVE 8 PSI
  • Ensure the faucet is in the on position to help relieve system pressure
  • Unscrew the three pre-filter housings and remove the filters
  • Clean each of the housings with soapy water and a brush and rinse out with cold water
  • Disconnect the inlet tubing to the membrane housing.  You may have to pull the membrane housing out of its clips to get a good grip. Use a membrane wrench or a car filter wrench, with a cloth, to unscrew the membrane housing cap
  • Use needle-nose pliers to pull out the membrane, while gently twisting, from the housing. DO NOT TOUCH THE MEMBRANE WITH YOUR HANDS.
  • Place the membrane on a clean plate or plastic while proceeding with the sanitizing process.  This assumes the membrane is still in good condition
  • Clean the membrane housing with soapy water and rinse
  • Replace the membrane housing cap by screwing on hand tight only
  • The post filter can remain in place as it will be replaced
  • Replace the second and third stage pre-filter housings, without the filters, hand tight only
  • Before replacing the first stage housing fill it about one third with regular water and add 0.5 ml (one teaspoon) of household bleach to the water
  • Replace the housing and ensure it is hand tight
  • Turn the faucet in the off position
  • Turn on the water supply and allow the entire system, including tank, to fill with the sanitizing solution.  This will take about 10 minutes
  • Turn the water supply off and let system stand for 20-30 minutes
  • Turn faucet in on position and allow the tank to drain completely.  The system is now sanitized
  • Proceed to remove housings and membrane housing cap
  • Fully drain all housings
  • Insert new filters.  Re-insert membrane and hand tighten all housings
  • The system should be run through three full tanks before re-using.  Each tank fill will take approximately two hours

We hope you found this article helpful.