Those of you using reverse osmosis filtering system's as I am. At what TDS do you typically change your RO filters? I asked the company I bought it from and they told me it depends on the individual. For our given application what would be the TDS reading to look for to change the filter? I really appreciate it.
Thanks,
Alex Mauney
Reply:
Those of you using reverse osmosis filtering system's as I am. At what TDS do you typically change your RO filters? I asked the company I bought it from and they told me it depends on the individual. For our given application what would be the TDS reading to look for to change the filter? I really appreciate it.
Thanks,
Alex Mauney
Reply:
Jess,
I've been using a ceramic filter for my water, but i'm still getting a little sediment in the tank. it comes out in the bottling filter, but i'm getting paranoid about it. what capacity RO unit are you using?
Reply:
I have an 1800 gpd RO. An inline tds meter is very inexpensive and very useful. I was told by the manufacturer that anything below 10 was considered purified water. Mine currently reads either 0 or 1 . The membranes aren't that expensive, so I'll probably get a new one if it goes up just a little, though I'm rather hoping that's at least a year. The pre-filters should be changed if the pressure difference before and after the filters increases more than 10 psi.
Reply:
Dave..what system did you buy? Or did you create something on your own?
Reply:
Dave..what system did you buy? Or did you create something on your own?
Reply:
Jess,
I've been using a ceramic filter for my water, but i'm still getting a little sediment in the tank. it comes out in the bottling filter, but i'm getting paranoid about it. what capacity RO unit are you using?
Reply:
I know this is an old thread, but the original post includes a timeless question that we typically answer for customers at least a couple times a week. If you check the specs on your RO membrane, you'll see something refered to as the "rejection rate." In many cases, the rejection rate will be something like 98 or 99%. This means that the membrane will "reject" (not allow to pass through to the purified water side) 98% or 99% of the TDS in the feedwater.
If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon filter do very little to remove dissolved solids. So with your tap water at 400 ppm, for example, you can measure the water at the “in” port on your RO membrane housing and you'll see it is still approximately 400 ppm.
The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 75 gpd Filmtec membrane has a rejection rate of 97 to 99% (i.e., they reject 99% of the dissolved solids in the feed water). So the purified water coming from your 75 gpd membrane would be about 8 ppm (a 98% reduction). To test the membrane, measure the TDS in the water coming into the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce purified water more slowly as their function declines.
So if someone has feedwater of 50 ppm, and you have feedwater of 650 ppm, you'll see there is not a specific number everyone can shoot for - it all depends on the tds of your feedwater and the specs your membrane.
Russ
