View Full Version : RO/Di Cartridges

04/15/2008, 06:29 PM
I was wondering when is a good time to switch out your ro/di cartridges? My TDS reads 0 after the DI. i ask this becasue the Sediment filter is turning pretty brown and the DI cartridge resin color is getting to that purple phase where it looks pretty much all used up. The carbon filter looks alright, no change that I see. I also have a flush kit on the unit to help exten membrane life.

I guess my question is whats the recommended time fram to change out for cartridges?

04/15/2008, 06:40 PM
The prefilter and the postfilter ill change every 6mon unless i notice something is not good. The membrane ill change once a year or if something isnt testing right ill change sooner.

04/15/2008, 06:50 PM
I thought you were suppose to get a few years from your ro/di membrane am I incorrect on this? I was thinking 6-12 months for the others but if the tds is still saying 0 should I change?

04/15/2008, 07:49 PM
Use the DI all the way up until you notice the TDS start to rise. The sediment is a very cheap filter so I would say every six months.

04/16/2008, 06:00 AM
Thanks that is great to here. What abiotu the membrane then? Just curious cause I am getting mixed reviews some say 2-4 years other sy a year, anyone have a definate answer on this?

04/16/2008, 07:08 AM
If you keep it flushed, you should get 3-5 years from a membrane. Of course, that also depends on your TDS from the input. Best way to measure is check tds prior to the water going into the DI bed. If your membrane is supposed to drop TDS by say, 90% and you've just flushed it and it's only reducing by 80% then it's probably time to replace the membrane. Please note that the numbers I gave are just for an example, not concrete for every given situation.

Roland Jacques
04/16/2008, 07:34 AM
sediment and carbon filter changes are dependant on YOUR tap water and how much water you use.

i use 20,000 gallon gulzler carbon they should last close to that if you use a 1 micron or less sediment filter before it. ( Im not sure how chloromine can effect carbon life)

Sediment filter can get cloged up very fast or not. that depends on if you have old pipes, high water sediment... the way i tell if my sediment prefilters need changing is i check the pressure drop, if the presuess below wher i want it (60psi for most) its time to chane the prefilters. Without a pressure gauge??? you just have to go by the way it looks?

personlly id change my membrane if it changed 2 or 3% if mine at 97% got down to 95% -94% id change it

04/16/2008, 02:08 PM
The general rule of thumb is 6 months for prefilters and carbon blocks. This is for several reasons. One is to reduce the likleyhood of bacteria or virus growth inside the housings which is a valid concern. Another is so you do not have any pressure restrictions to the membrane causing reduced production. Yet another is carbon blocks have a limited life for adsorbing chlorine and volatile organics. As Roland pointed out there are better carbon blocks which will probably last longer than the 6 months though.

Another method is to use prtessuer gauges and a low level chlorien test kit and monitor the filters conditions but most of us don't pay close enough attention so the 6 months rule is the better alternative.

Be sure to disinfect the unit while you have it apart to play it safe.

04/16/2008, 03:55 PM
Well that all great info.By the looks of the sediment filter it probably needs changing along with the carbon and DI I would assume. have to check my log when I started using it. My TDS reads 110- 120 before and always 0 after the Di and I think I have had this running 6 plus months maybe will have to check in on that. Thanks for the membrane tip I thought it was 2-4 but 3-5 is even better cause they are expensive themselves.

04/16/2008, 07:55 PM
The better the prefilter and carbon blocks you use the longer the membrane will last. Cheaper filters can be about as effective as a screen door so you can imagine what gets passed on to the RO membrane. If you do not keep the waste ratio at 4:1 or more it begins to build up and solidify on the membranes surface rendering it useless over time. Buy the best filters you can afford and its not uncommon to have a membrane go 7 to 9 years or more even with heavy use. That plus better filters allow the membrane to do its job better which also makes DI resin last longer which is another long term cost savings.

04/17/2008, 03:45 PM
Thanks for all the help.