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How to Flush and Sanitize an APEC Reverse Osmosis (RO) – 90 system

When the RO system and tank are contaminated, they need to be thoroughly flushed and sanitized before putting in new filter cartridges, and restoring the system back to use. Please follow the steps below to clean out the RO system and tank.

Basically, we will drain out the old water in the tank. Take out all the old filters to empty out the housings. Put some bleach (chlorine) into stage-1 housing, and then close up all the housings. Feed cold water into the RO system, which will send the chlorine to all parts of the system. Then allow the chlorinated water to stay (soak) in the RO and tank for about 5 hours to disinfect and sanitize. Then drain out the chlorine water from RO and tank. Put in all new filters, new membrane, and replace any old valves if necessary at this point. After the new filters are in place, start the RO system and let it run as usual.

Make sure to throw out the first 2 tanks of water to flush out the new filters. This procedure will clean the RO system and get it back to good shape again.

Below are step by step instructions to help you sanitized the RO system:

  1. Turn off the Cold water supply connected to the RO.
  2. Drain out the old tank of water, through the dispensing faucet.
  3. Take out stages 1, 2, 3 pre-filters from their housings. Also, remove the Membrane from its housing.  (If you plan to re-use the membrane, use pliers to take out the membrane, avoid touching it with your fingers to prevent contamination.)
  4. Do not remove the last filter (stage-5). Leave this filter on as is at this point.
  5. Wash the 3 housings with mild soap. When washing, make sure not to lose the O-ring on the housing.
  6. Put ½ cup of bleach (chlorine) into the Stage-1 housing. Screw this empty housing back onto the RO head, with bleach inside.  (When you turn on the feed water later, the bleach in this housing will flow through the entire RO system and tank, and sanitize the system that way.)
  7. Put the stage 2 & 3 housings back onto the RO frame, tighten them. Then, close up the Membrane housing cap, without membrane inside.  Now, all 4 housings for stages 1, 2, 3, & 4 are empty canisters waiting to be filled with chlorinated water.
  8. Turn ON the cold water supply to feed water into the RO.  Open the tank’s valve to allow water into the tank.  Let the raw water run through the RO and fill the tank as usual. Since all the housings are empty, the tank should fill up rather quickly (a few minutes). When the tank is full, the RO system will shut off.  When the system shuts off, the waste water in the Black drain line will stop running, or you won’t hear it draining any more.  
  9. Now the chlorinated water has filled all the lines, housings, and tank of the RO system. Allow the chlorine water to stay in the system for 2-3 hours.
  10. To make sure that no feed water enters the RO system during the 2-3 hours soaking time. Turn off the feed water to the RO by closing the Needle Valve located on the side of the Feed Water Adaptor. Turn needle valve clockwise until tight to shut-off water.  Closing the needle valve cuts off the RO’s feed water without cutting off the Cold water supply to your sink faucet.
  11. After 2-3 hours soaking time, open the tank valve, turn on the RO faucet (lift faucet lever into locked position) to drain out all water from the tank.
  12. Open up all the pre-filter housings and the membrane housing, drain out all chlorine water. To ensure proper disinfecting, DO NOT rinse the housings.
  13. Now the system and tank are cleaned and sanitized. Proceed to install all new filters and membrane.  Replace the stage-5 filter at this time. If the old Check Valve or the old Auto-Shut-Off valve needs replacing, then replace them at this time as well.  Follow the “Filter Change Instructions” to replace the filters.
  14. After putting in all new filters (and valves), turn on the feed water.  To open the Needle Valve turn needle counter-clockwise.
  15. Let the tank fill up (takes 2-3 hours). Before using the pure water, drain out the first 2-3 tanks of filtered water to flush out the new filters and any residual chlorine.

Congratulations! You’ve successfully cleaned out your RO system. It’s now ready for your enjoyment and use.

If the issue was not addressed, please contact us at:
800-880-4808, or

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