Servicing a Generic Reverse Osmosis System

Purpose

To change the RO filter cartridges, and clean and sanitize the system.

Tools and Supplies Needed

• Pre and post filter cartridge replacements. Note that sometimes an RO has an "inline" post filter - make sure you replace this as well
• Catch pan - to catch the water that tends to spill when removing old filters and the various water lines that connect the different parts of the system.
• Chlorine - a couple of ounces for sanitizing (plain, unscented Clorox is best).
• Paper towel or a clean cloth or rag.
• TDS hand held tester and clean cup.
• Bicycle pump
• Air pressure gauge (you need a good one that can measure accurately in the 5psi range - the ones for cars that are pencil shaped will not work)

A Few Notes on Reverse Osmosis Units

• RO units can have either a CTA membrane or a TFC. Most units these days are TFC
• A TFC membrane requires that all the chlorine is removed before the water contacts the membrane; therefore, if your water supply is a chlorinated city sourse, at least one prefilter needs to be carbon or KDF based.
• If your unit has a CTA membrane, you need to make sure that you do not have a carbon filter ahead of the membrane. You want chlorinated water to contact the membrane
• There are a number of cheap RO units being sold these days - they may skimp on certain components and lack a shut off valve on top of the storage tank. We suggest that you obtain one and retrofit it. It makes servicing much easier. As a matter of fact, it is very difficult to properly service the unit without one!
• Some manufacturers recommend routine changing of the membrane every 2 years. We have seen membranes perform excellently for as long as 8-9 years. We have also seen them fail within 2-3 months. The only way to know how yours is doing is to test it. See *** below.

Procedure

Please note: The *, **, etc. all indicate further notes. These are found at the end of the Procedure list.

1. Perform TDS test on RO water*** (to verify membrane function).
2. Verify that the shut off valve is working. If your RO has been installed in a standard manner, the faucet will also act as an "air gap" and when the unit is operating, there will be a small stream of water flowing through the hole under the faucet handle.
   • Check to see if water is flowing - if not, the shut off valve is working fine.
   • If it is flowing, shut off the valve on top of the the storage tank. Then, watch to see that the flow comes to a slow drip or stops altogether. If this flow does not stop, either the shut off valve is malfunctioning or there is another problem with the system and you will need a service call by a professional.
3. Turn off water supply to the RO.
4. Turn off valve on top of the storage tank.
5. Open RO faucet to relieve pressure.
6. Remove line from valve on the storage tank (Have catch tray ready to catch dripping water from line once it is removed.)
7. Remove storage tank and drain all the water into sink by opening valve.
8. Test the pressure of the tank - maintain at 5-7 psi. (use a good quality gauge - see above) Pump more air in if necessary.
9. Sanitize the tank. This procedure is necessary to keep bacteria/off tastes, etc from gaining a foothold in the tank.
   • You will need whatever tubing and connectors* necessary to connect the supply line directly to the storage tank.
   • Carefully pour about 1 tablespoon of bleach into this tubing being careful to handle so the bleach stays in.
   • Complete the connection from the supply to the tank
   • Turn on water at supply stop to fill the storage tank; make sure tank valve is open.
   • Once the storage tank is full -- it will take several minutes -- turn off the supply line, turn off the tank valve and disconnect the tubing.
   • Reconnect supply line and tank line to their original configurations
   • Leave the tank valve closed for now.
10. Remove pre and post filter cartridges. Sump wrenches are typically supplied with the RO system. (Can be done while storage tank is filling - have catch tray positioned underneath the filters.).
    • You should clean the sump with dish soap and a brush or sponge. Be careful of any o-rings in the sump, not to wipe any of the lubricant off them.
    • Make sure there are no gaskets in the bottom of the sump from the old cartridge
    • Sanitize the sumps with a very dilute bleach solution - teaspoon of bleach per sump and fill
    • Let sit for a couple of minutes, then dump solution out
    • If the oring is dry, lubricate with a good silicone lube - do not use vaseline, it can swell the oring
11. Install new filter cartridges.
12. Flush the membrane. Depending on the configuration of the RO system, this will either be a straightforward step or complex enough to decide to skip it!
    • There will be a flow restrictor on the drain line from the membrane.
    • If this restrictor (often a 3" white cylinder) is on the drain line and removable, go ahead and remove it.
    • Direct the remaining line attached to the membrane into the catch pan and go to #13.
    • If this restrictor is not obvious, it may be integrated into the membrane and you will need to skip the membrane flushing step and go to #16.
13. At this point, turn on water at supply stop while holding the drain line. What happens is that water in the membrane will pass through the unrestricted drain line followed by a burst of air, and then more water with some carbon particles in it. This is done to 'blow' the system of air and then carbon 'dust' from the new pre-filter. The membrane appreciates this.
14. Continue flushing for 10 seconds or so then turn off the water at the supply stop.
15. Allow any water in the drain line to drain out, then reconnect the flow restrictor in the original configuration.
16. If you have a monitor, check the batteries with a battery tester and replace if necessary.
17. Open supply stop to run water into system and pressurize it. (All lines are connected at this point, just the way it was before you began the service procedures.)
18. Open the faucet, and then open and close the storage tank valve a few times to let air out of the line. Do this until only water is flowing from the faucet. Close faucet and tank valve. Let system stand for several minutes.
19. Check for leaks**** at connections where you disconnected and reconnected lines, and at the filter cartridges.
20. Open the faucet and tank valve again and let all the water drain out of the storage tank. Don't drink this water or give it to your plants. When the flow has slowed to a trickle, shut off the RO faucet.
21. Let the storage tank refill with water. This will take about 4-5 hours. Then drain this water. Again, don't drink this water or give it to the plants.
22. After this, your storage tank will again refill with water. This water is good to drink. Your system is now back to normal.

* Sometimes connectors are the quick connect type that require handling in a specific fashion. To connect::

• Push the tube into the fitting about 1/4-3/8". You will feel it bump up against a "stop"
• Push the tube an additional about 1/4-3/8". It will push past that first stop and then bottom out at a second stop. It is now inserted correctly.
• NOTE: if you don't get the tube to the 2nd stop, it will leak**** a lot.

** To disconnect the quick-connect type fittings::

• Push the line towards the connector, grab hold of the plastic "collet", and then pull the line away from the connector. It should disconnect easily. If it doesn't, make sure you hold the collet tightly against the connector and pull the line a little harder.
• NOTE: the difficulty always occurs because the collet isn't held tightly against the connector body.

*** Testing the Membrane and Interpreting the TDS results:

• The TDS tester measures total dissolved solids in the water. The RO membrane is functioning when the TDS reading for the drinking water from the RO faucet is less than 25% of the TDS reading of the tap water.
• We sell TDS testers for $50.
• For example, the TDS for the drinking water is 35 and the reading for the tap water is 300. The membrane is functioning as it should. However, if the TDS for the RO water is 75 or above, then the membrane is considering to be ineffectively functioning and needs to be changed. Call a water technician for this job, and wait to change the filters until the membrane is changed.

**** What to do if you find a leak:

• If you have quick-connect fittings, make sure that the water line (tube) is correctly inserted into the fitting. Sometimes, it isn't pushed in deeply enough, even though it felt like it was.
• If that doesn't work, then jiggle and push the line in the fitting. Sometimes this works.
• If not, then reposition the equipment (usually the storage tank) in the position it was before you began servicing the system. Then repeat the above steps.
• If that doesn't work, call us. The fitting is probably faulty.
• If you have other types of fittings, there may be a crack in the tube at the fitting and you may have to redo the fitting. Make sure you have the proper inserts and ferrules or you will be dealing with worse problems down the road.
• With filter cartridge housings, sometimes you can get a leak at the connection between the sump and the filter head. Pull the sump off and examine the oring. Make sure there is no debris on the oring and relubricate with a good silicone grease. Remount and tighten hand tight. Do not overtighten - you can crack the sump and have a catastrophic leak on your hands.

 

return to top

Winner of a Gold Star Certificate from BBB Denver/Boulder, 2007 - for having no complaints in the three-year period, 2005-2007.