How Often Should I Change My RO Filters?

How Often Should I Change My RO Filters?
By Mark Timmons
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How Often Should I Change My RO Filters?

John asks:
I have a water softener and a pre-filter ahead of my Reverse Osmosis System.  How often should I change the filters?
The Water Doctor replied: Water quality varies so much that it is impossible to give you an accurate answer.  For example, some water is more turbid and contains more solids.  Water that looks substantially the same could plug a filter in a month... or a year.  The thing is, you don't want to wait until the filter is plugged, you want to changed it before solids or chlorine comes through.  On hard water, I have seen membranes last six months to a year and on soft water, they can easily last three to five years. In my own personal case, I have one of THESE in my home. I test the water hardness and chlorine levels on a weekly basis and these the RO for TDS levels multiple times a week.  The only way you can know if your membrane needs changed is by testing the TDS and when it drops to below 80% rejection, it is time to change it.  By testing the softness of the water, you can know how well it is working and adjust it to meet your needs. In many cases you can change the RO Filters on a yearly basis, if you have soft water and proper pre-filtration, but it never hurts to do it more often.  After all, this is your drinking water we are talking about. For whole-house filtration, the absolute best filtration is a 5 micron "Pleated" filter like THIS. At the very minimum, if you have a water softener, you should at least have a test kit to test the hardness, like this: https://www.uswatersystems.com/hardness-field-analysis-test-kit-2403.html It is good for 50 tests, so if you test your water once a week, it will last a year and then the testing chemicals can be replenished HERE. THe professional grade test kit includes tests for pH, iron, chlorine and TDS, but you can also buy a TDS meter HERE.  Everyone that has a reverse osmosis system should have a TDS meter and this is a professional-grade model that lasts for years.  You wouldn't dream of having a furnace or air conditioner without a thermostat - why on earth would you have a reverse osmosis system without a TDS meter?  Think about that! Here is the LINK to all of our water testing products.
November 23, 2014
Comments
steve
December 6, 2017 at 5:45 PM
hello water doctor, my R/o unit still has a very low reading on the TDSmeter however the nitrates in the water are going up, so im presuming that one of the filters is passed its best, but which one do i replace. Im useing the water for marine fish by the way so dont want any nitrates really can you advise
Mark Timmons
December 6, 2017 at 8:58 PM
What kind of RO do you have?
Kevin M.
January 26, 2018 at 2:50 PM
The link in the next to last paragraph does not work. https://www.uswatersystems.com/tds-3-hm-digital-tds-meter-with-carrying-case.html
Mark Timmons
January 29, 2018 at 11:35 AM
Thank you - it works now.
David Craig
April 3, 2018 at 2:50 PM
Hello Water Dr. Just bought a house with a RO system, tap water is 750 TDS on the RO was 750. Fail. Replace all filters, sediment 2 carbon blocks, post and membrane. Able to get TDS meter down to 135, that's rejection rate of 82. Any ideas?
Mark Timmons
April 4, 2018 at 11:26 AM
1. Membrane is not pushed all the way in; 2. Bad membrane; or 3. If it is a permeate pump system, you have TDS creep.
David Craig
April 5, 2018 at 11:09 AM
Thanks Mark I'll try replacing the membrane again. I'll let you know if I get the TDS down 2 a reasonable reading
yoganand
June 24, 2018 at 2:52 AM
Hello water doctor i have a water purifier (UF+ RO+UV). TDS of tap water is 350 and filtered water is 50. shall i have to change the filters. filters were installed 9 months back. plz clarify,, yoganand
Mark Timmons
June 24, 2018 at 3:22 PM
The TDS has little to do with changing filters, although if you don;t change the filters at appropriate intervals, the membrane will be damaged due to sediment or chlorine. Filters should be changed at least once a year... Every 6 months if the water is really bad. - The TDS is what the membrane reduces and you need a TDS Meter to determine how well the membrane is working: https://www.uswatersystems.com/ap-1-hm-digital-aquapro-water-quality-tester-tds.html
Ross Welburn
January 17, 2019 at 2:16 AM
I’m on a well and use a water softener. The Softened water is 66ppm and the RO water is 7ppm. The RO membrane is 15 years old. We have no chlorine in our water, I just dont like the taste of softened water. Is those reasonable numbers? Tks, Ross
Mark Timmons
January 17, 2019 at 6:40 PM
Those are good numbers but I would replace the membrane and filters. Hetrotrophic bacteria are a problem in an RO System. You can use this as a final filter to kill bacteria: https://www.uswatersystems.com/us-water-pulsar-quantum-disinfection-cartridge-for-ro-systems.html
Melani Wendling
April 9, 2019 at 1:06 PM
Could a person get sick on the water if the filters aren't changed?
Mark Timmons
April 12, 2019 at 3:04 PM
Yes, it is certainly possible.
Vicki
July 15, 2019 at 6:06 PM
I have a Culligan soft water and RO system. I am the only one in the house so how often do you suggest I have the filters changed. I am not able to do it myself and because Culligan is the only one that I can get filters from I am kinda stuck having them service it also,and it is expensive, so what do you suggest is an good interval?
Mark Timmons
July 18, 2019 at 7:08 PM
I always suggest once a year.