This topic may have been discussed before, but I couldn’t find a thread that dealt with it.
What are the parameters for changing an RO filter? I have a Xero Pure that is putting out about 56 TDS from the RO with an input TDS of 350. I have read that the RO is supposed to be 95 - 98% efficient. So what is the low end of the allowable TDS from an RO membrane?
While we are on the subject of the Xero Pure, I noticed a reduced output from the DI tank. I pulled off the brass fitting on the outlet side, and discovered that the fitting is basically blind, with 4 tiny pinholes in it, about the same bore as the wire in a paper clip in diameter. What is the purpose of that deliberate choking of the flow? I get that the RO needs pressure to work properly, but what is the purpose of increasing the pressure inside the DI tank and drastically reducing output? Can I just replace the OEM brass outlet fitting with something that does not restrict flow at all?
I would appreciate hearing from you pure water nerds out there. Thanks in advance for your wisdom and input.
I remember it being 50%. so if your tds is 350, you’re still good until it’s at 175. My tds here is also around the same as yours , my Ro is about 30 right now .
I change my out my RO membrane once every two years. I have 150 incoming tds and get 99% pure rejection for about the first 6 months. During this time I don’t bother using DI resin because it’s coming out at 001-002 ppm. At about one year in it increases to 005-007 ppm and this is time to use DI resin.
At the end of the two year cycle I’ve got about a 85-90% rejection rate. At that point I change the RO membrane out and sell it.
If your TDS is only getting down to 56 from 350 you’re operating at around 83% and I’d recommend changing it out. How old is the RO membrane?
And the DI is restricted to maintain pressure in the DI housing to eliminate channeling. With TDS readings as high as you’re getting out of the RO, you could easily get channeling through the DI if you remove that regulator.
My system is 6 years old and is still discharging @ 5 TDS through the RO, I’ve changed out my DI twice since new. I use a 60 gal. tank only system which is always filled from my house (which is around 400) so I would estimate I only produce 2500gal of treated water through it in a year. Not sure the ratio of gallons used compared to gallons produced, but I would imagine 4:1 or 5:1? If I recall, WCR had a 3rd party a few years back who was able to refurbish an RO membrane @Chris@Alex@John?
If incoming tds is 100 ppm and it’s 002 ppm coming out of the pure water side of the RO then the membrane is filtering 98 out of 100 ppm impurities from the water. That’s a 98% filtration.
Incoming TDS minus outgoing TDS divided by incoming TDS multiplied by 100 = % of rejection.
Example: 300 incoming TDS minus 5 output TDS = 295 divided by 300 = .98333 x 100 = 98.33% rejection.
When to change the RO is dependant on your cost/frequency to change out the DI. If you use your system everyday and Resin need refilling every couple of weeks, then I’d change it. If you don’t use your system too much and you can go a couple months or more between changes then I’d say keep going with your existing RO.
on this thread.
