How to Maintain a Reverse Osmosis System

How to maintain a reverse osmosis system blog header

How to Maintain a Reverse Osmosis System

Reverse Osmosis water filtration is one of the most popular forms of water treatment. So what does it take to MAINTAIN a reverse osmosis system?

How often do RO filters need to be changed?

For optimum efficiency, routine maintenance should be performed on reverse osmosis systems.

Reverse Osmosis maintenance tipsAs a rule of thumb, RO systems have three, four or five-filter stages. Without detailing each stage of the RO process (since the number of stages varies based on the model), we outline here some basic maintenance information that applies to most RO units.

First: In order to protect the delicate RO membranes, water first flows through a pre-filter. This pre-filter cartridge is designed to filter out dirt, silt, sand and other sediments. This pre-filter should be changed every 6-9 months. If not properly maintained or changed on schedule, the pre-filter can foul or become clogged, thereby making it unable to protect the RO membranes.

Second: The next phase is generally a carbon filter which is designed to remove chlorine and other taste or odor contaminants. This is important because chlorine can ruin the RO membrane. This carbon filter should be replaced every 6-9 months, also.

>>>Not sure how much chlorine is in your water? Request a FREE Water Test from an authorized WaterTech dealer near you.

Third: This is the actual reverse osmosis phase. Reverse osmosis (RO) is a separation process that uses pressure to force water through a membrane. The membrane retains the contaminant on one side and allows the pure solvent (water) to pass through to the other side.

This process is the reverse of the normal ‘osmosis process’, which is the natural movement of solvent from an area of low solute concentration, through a membrane, to an area of high solute concentration when no external pressure is applied.

Water passes through the RO membrane at generally 35 pounds per square inch (psi). At this rate, roughly two drops per second. The contaminants rejected by the membrane are piped down the drain.  RO membranes should be replaced every 2-3 years.

NOTE that filter and membrane lifespan will vary based upon local water conditions and household usage.

Fourth: Finally, a carbon filter stage is usually added to “polish” off the water at the end of the cycle. This stage removes any remaining taste or odors to create outstanding drinking water. The carbon filter should be changed every 6-9 months.

What if I forget to change the filters?

Reverse Osmosis RO PureMAX II WaterTech

If you forget to change the filter, over time the system will begin to produce less and less water, ultimately not producing water at all.  Decrease in water production is a strong indicator that you have reached the end of the filter and membrane useful life.

Thus, it’s always a good idea to set a reminder and change the filters and membranes on schedule.

Do I need to clean an RO system?

Yes, a system sanitization and recharge should be completed annually. Your local water treatment professional can provide this maintenance service or consult your RO system’s owner’s manual.

How long should a RO system last (lifespan)?

If a reverse osmosis system is serviced and maintained as parts wear out (like the faucet and storage tank), the system can last for years, 10 to 15 years is very possible!  Make sure to follow the membrane filter schedule and sterilize/clean the system annually.

Will A Water Softener Hurt an RO System?

No, a softener and an R.O. system are actually a great combination. The softener will soften the water throughout the home, AND the RO system will remove 98% of all sodium in the water. This duo makes for great-tasting drinking water.

Because calcium and magnesium, the minerals that make water hard, are difficult minerals for an R.O. membrane to remove, the softener acts as a protective barrier for the RO system. This protection keeps the RO system from fouling and can extend the life of the membrane.

How Can I Purchase an RO System?

If you have more questions about RO technology and/or systems, contact a local WaterTech dealer. WaterTech’s RO PureMAX II is the most advanced point-of-use, under-counter RO system with a push-button monitor that gives you filtered, delicious water for your entire household.find a watertech dealer




  • I have well water high in iron lately i can still taste the well water after its been through the system n the filters have been changed what should i do

  • I find experts in water treatment at the retail level disagree on issues resulting in a difficult time knowing what an expert is…can you help me?

    I purchased a home that has a 5 year old (6) stage RO system that works very will. Our community has several wells at differing depths which cause water characteristics to change by the season and water table along with all the differing abatement protocols for each well. The tap water is (very) heavy in chlorine (over pumping on well #14) during the spring and fall of the year however the RO flow is good and the water is great tasting.

    I believe a sediment filter is totally used up when the flow decreases to unacceptable levels (long system recovery time)(in industry, a filters efficiency increases as used while flow decreases) is this correct in RO systems?

    I believe an RO membrane would be considered used up if the recovery time (tank charge time) were to become unacceptable (aside from renewing tank air charge annually), is this correct?

    I believe if water is coming out of an RO system, the water is at peak quality (aside from the activated carbon filter saturation level)(a drift in odor and/or taste with OK flow), is this a correct assumption?

    Basically, is flow rate the measure of performance (maintenance trigger) since an RO system has no dynamics and the carbon phase needs changing when odor or taste drift?

    Thank you for any help,

  • After installing new pre-filter, a new carbon filter and a new membrane, is it safe to drink the water right away? Also, based on what I read in the article, change the pre-filter and carbon filter every 9 months but the membrane once every 2-3 years?

    • Isaac Linton, CWS I

      Yes, you can start drinking the water right after filter changes. And you have it correct– that the RO membranes don’t need to be changed out nearly as often as carbon and sediment filters unless they’ve been damaged or fouled. Let us know if you have additional questions.

  • I purchased a new home with a RO system already installed. I had my husband replace all the filters and membrane and sanitized it. But when the water comes out, I can see small tiny particles in the glass. Also, I see a “sudsy” layer on the surface of the water as well. What else do you think needs to be done?

    Thanks so much!

    • Isaac Linton, CWS I

      Hi May: it’s hard to know what the problem is without seeing the system. Perhaps even though you’ve changed out the filters, if water sat in the tank for a while, perhaps bacteria started growing and you’re seeing particles from some gunk built up in the tank? You could trying filling and draining the tank a couple of times to see if the tiny particles you’re seeing are flushed away. You might also want to call a water treatment professional for service and/or to test your water. Hope that helps.

  • I replaced all 4 filters and after 24 hours there’s still a limited flow and not much capacity after a few cups. Is there some way to reset the reserve tank?


    • Isaac Linton, CWS I

      You can check the pressure in the holding tank. It has a stem valve similar to a bike tire. It should be between 5-7 psi. Sounds like the bladder may have ruptured in the tank and you will probably need to replace it. I would recommend having a water specialist look at it.

  • Thank you for your information on RO systems.

  • I replaced the filters and the membrane. Did the flush and now I tast the carbon. Is that normal?

    • Isaac Linton, CWS I

      We recommend letting the RO tank fill 2-3 times and flush it before use. It can take a few hours to fill the tank. Try that again, and if you still are tasting carbon, please give us a call (if you purchased from ESP Water Products) or contact the company that sold you the RO system.

  • Does the RO system need to be used often? We would like to purchase one for the house but we can be gone for up to 6 weeks. Can the filters go bad leaving them unused for this long or any bacteria or mold grow?

    • Isaac Linton, CWS I

      If you leave the system for a few weeks you will be fine. If longer you will need to drain tank and replace filters as bacteria will grow.

  • My RO has slimy gunk clogging the opening where the water comes out. What could it be, how do I clean it and get rid of it?

  • I have recently replaced pre-filter candle. After replacement, I am observing that the force of water that draining out is slow and water production is also very slow. Before replacement, it was ok. What might be the problem ?

    • Isaac Linton, CWS I

      We’d recommend having your local water treatment specialists check out your system. There could be clogging or other issues that are causing the change in water flow. You can find the local WaterTech dealer in your area at

  • We bought a house with an RO system and soft water installed. The filters were changed about a year ago and the house was not occupied during the time they were installed and when we bought the house (so the system was not used). I flushed the tank 2 times, and there were particles at first, but after another flush, there are none. It is an older system, approximately 10 or so years old (the tank). As the filters sat for so long with no use, is it safe to use? The water is delicious, but no one is drinking it regularly. I just took a sip. Thank you for any feedback you may have.

  • I need to make corrections to my post of a few minutes ago. The filters on the HO system were replaced 5 months before we bought the house and it was used sporadically. We have not used the system since buying the house 7 months as we were not sure if it was safe and it is lower on the list of having it checked out with other necessary changes we are making. Thank you very much!

    • Isaac Linton, CWS I

      Hi Leigh, anytime you have sitting water, it’s likely you’ll have bacteria growth–could be in tubing, tank, filters, and membranes. I would contact your local WaterTech dealer or water treatment specialist for assistance in sanitizing your system and getting the needed replacement filters. Find a local WaterTech dealer here:

      • You are so kind to reply to my email. Thank you for this and the link. We will have it checked out.

  • I have a three stage RO (pre-filter —> membrane —> post-filter). My water also goes through a house-wide water softener prior to the RO. There is no difference between the pre-filter and post-filter for my RO; a set of two costs about $40.

    Someone suggested, as a way of saving money, that when it’s time to replace the filters that I move the old post-filter to the pre-filter location, and put in a new post-filter. Their contention is that old post-filter has much more life left in it than the old pre-filter. Is there any truth to this (and would you recommend doing this)?

    • Isaac Linton, CWS I

      That can work, if you want to save a few dollars. Seems logical.

    • Probably a better idea to just replace the post filter every other time. You will want a new prefilter since that’s the important one.

  • I purchased 5 stages filter 7 years ago, i’m replacing all kandles regularly, just want to make sure if the water tank needs to be changed routinely at some time?

    • Isaac Linton, CWS I

      It’s hard to say, Islam. The quality of the RO unit you purchased plays a big part in this. Like anything, a water tank can wear out. I would contact the manufacturer of your RO system to find out what is covered and what the life expectancy is on your particular system.

  • I have purchased 7 stage filter connected to soft water, two years back. My engineer replaced RO saying it has to be replaced every year.Now that, he removed prefilter and given direct connection to to carbon filter. will it damage my water purifier? Is this the correct process of maintenance? else to grab money intentionally in this way? Because, the above valuable replies given by you envisages that the recommended period for replacing RO is 2yrs and for prefilters&carbon filters is 6-9months. Kindly reply.

    • Isaac Linton, CWS I

      WaterTech doesn’t sell a 7-stage filter system. We’d recommend you go directly to the filter system manufacturer to find out how often they recommend replacing the filters. One year is a standard replacement time, but that all depends on the filters being used, the quality of water, and the system usage.

    • There are cheap TDS readers online (for $10 to $20). If the TDS is below say 50, you don’t need a new RO membrane. You might get 5 or more years out of the RO membrane, so the tester will save you money and tell you when it’s actually no longer working.

  • Hi, hoping I can get help from anyone here about our RO system. I found this page while searching Google for help. I read the above comments and my issue is not exactly covered. First off, our RO was sold & installed by a local guy that did the work on the side & came highly recommended. Our water here, in extreme rural north central Kansas, is terrible. It’s very hard & dirty. In fact, they tell us a child must be at least 2 years of age before drinking it. (Yikes!). Also our membrane only lasts 2 years (& that’s pushing it). We have a 3 (or 4?) stage Microline TFC435. The system is 13 years old. We were told the unit will not go bad & we just have to change filters as needed. We do the pre & post & carbon bullet thing every 6 months. Currently we are getting very low flow from the spigot. The membrane was replaced in Jan of this year (16) & the pre, post, & bullet thing were replaced in June. I have taken both the holding tanks out and drained them & put 7 #’s of air in them. It’s been 24 hours & it’s still flowing very slowly, just above a trickle – a very light/slow/small stream. the only other thing I can think to add is the other weekend we had very little pressure all throughout the house. No one around us (neighbors) experienced this & the water meter wasn’t moving much at all. Then it cleared up. Later it appeared again & then again went away. A few days later once more it happened again & cleared up again. It has not happened again for over a week. The house was built in ’76. Hope I have provided enough information for whoever is kind enough to help me figure out what to do. Thank you.

    • Updating: There is no water flow at all now & I have double checked to make sure all the valves are open.

  • My ro is giving output of 8 tds. Rejected waste water has tds of 300. Is the rejection too much. Will maintaining such low tds reduce the life of the membrane. What flow rate or tds should be maintained to maximise membrane life and yet have safe drinking water

    • Isaac Linton, CWS I

      There’s no way to regulate how much/little TDS is removed. It sounds like your reverse osmosis system is working correctly.

  • Dean Christianson

    I have a 16 year old U.S. Water Filter RO system that probably hasn’t been serviced in 2-3 years or more. Used to have the company service it once a year, but for some reason that servicing stopped and we just pressed the check button every so often and it was always green, so we didn’t do anything with it. Started reading about needing to change filters every 6-9 months… so I don’t know if we can even find filters to replace or should we scrap the system we have and go with a new system??? If so… what brand of system would be best????

    • Isaac Linton, CWS I

      Hi Dean: That’s great that your unit lasted 16 years! But since the unit is 16 years old, you are right that it might be best to replace the entire RO system. RO systems are pretty reasonably priced, so they’re generally not too painful to replace. And the good news is, the newer models are more efficient and use less water during the filtering process, are generally quieter, and overall produce great-tasting water.

  • Good tips, thank you! Just wrote a similar how-to article on this if you’re interested:

  • I have sent my backwash drain to discharge into the back yard as my sewer drains into a holding tank which is expensive to get pumped out, is there any contaminants in backwash cycle that are detrimental to the environment?

    • Isaac Linton, CWS I

      Hi Terry, Discharge water is two-fold, it’s water that is used to rinse the RO membrane to keep contaminants off and secondly, it’s water that contains the rejected contaminants. Whether or not the drainage water is contaminating your backyard will depend on your source water (how contaminated is the water?) that is getting rejected by your RO system. As for drainage, always follow your local or city code. Check on what they allow.

  • Good work done ,i have water purifier which has 6 reverses osmosis membrane it delivery 1200 per has developed problem which out put drinking water is dirty , but has same particle, how can i maintenance it so that out put water is clean?,

    • Isaac Linton, CWS I

      Hi John: Your RO system has 6 membranes? Follow the instructions on the blog for cleaning a typical system. If you have a larger system, we recommend that you contact the manufacturer or refer to your system’s maintenance guide for cleaning instructions specific to your system.

  • What is in the GE Sanitation filters for a GE 3 cartridge reverse osmosis system?
    They look pretty inert. Instructions for use say to add 1 ounce chlorox to it. Can they be used more than once?

    • Isaac Linton, CWS I

      Hi Brian: We do not make/sell the GE 3 cartridge RO system so don’t know much about it. Contact GE directly. Thanks.

  • We had very low water pressure coming to the house because of servicing to the system. This went on for about a week. During this time, our r.o. Water began to taste foul. Could the low pressure have a bad effect on the r.o system?
    We are replacing the two pre- filters. Do you think we may need to replace the membrane? The house was vacant for 7 months in the summer.

    • Colette McCullough

      Starting with the 2 pre-filters is a good idea. If you don’t see an improvement in taste, call your local WaterTech dealer
      Or you may simply need to clean and sanitize your RO system. I would start there before replacing the membranes.