RO/DI Filters

Prefilters and carbons should be changed every 6 months and the system disinfected at that time. RO membranes can go between 18 months depending on how often you do the above and the quality of the repacements you use. DI resin is entirelye dependent on how well your membrane is working, if you have CO2 in your water and how much you make. I have a Spectrapure MaxCap and just changed only my second DI cartridge in 26 months and thats with a 100G and 16G nano.
The average system wil not do that but you can probably expect around 300 gallons out of a vertical DI.
Do not rely on color changing DI resins though, you need a $20 TDS meter to judge condition, color change is very unreliable.

 

Well I will tell a bit more about my setup. All I have at this moment in time is just a 150g tank and stand....... Ahhh and just a bit of research knowledge and questions ;D

 

So From what i gather is that if you do regular maintenance on your RO/DI itll work longer. How do you disinfect a RO/DI? Would that be taking the cups off and wiping them out with pure water and a towel?

Now ive heard alot about Co2. What are you revering to with RO/DI?

 

A TDS meter is the only true way to tell how the unit is performing. I usually have to change the sediment filter every 3 months and 6 for the carbon blocks/di resin. The di is tricky because as it wears it deteriorates and forms channels for the water to flow through reducing it's effectiveness dramatically. At least that's been my experience.

 

All vendors should provide disinfection directions with a new unit. I would check with your vendor. Basically it involves removing the prefilter and carbon(s), adding two tablespoons of regular unscented bleach, reinstall the empty housings, disconnect the line from the carbon up to the RO membrane so you don't get any bleach on the membrane then opening up the water supply to fil the housings. Let it sit about 5 minutes then open the supply again and flush it out until all smell of chlorine is gone.
When installing new the new filters arfter disinfection, or any replacements, flush the filters one at a time to remove all traces of antimicrobial treatments, glues, binders and carbon dust. Install only the prefilter first and flush it out the line you previously removed from the RO membrane. Next install the carbon and do the same flush. If you have two carbons then instal the second one and do a flush before hooking back to the RO membrane. These steps will all extend the life of your membrane.

Again a TDS meter tells you nothing about the condition of your prefilter and carbon, only the membrane and DI resin.

 

I've been using a Vertex 100 GPD unit RO/DI. It's been reading TDS reads 0 PPM for almost 6 months, but now its up to 1-2 PPM.

- At what TDS number do you start to worry and change filters?

Also, would the first step to do is change the sediment and carbon first. And if it reads 0 PPM, then RO and DI is still good? Or is it better practice to change our sediment, carbon, and DI all at same time? RO usually lasts about double-triple that?

 

You need 3 TDS numbers to calculate your RO rejection rate (removal efficiency) and your DI condition. Tap water TDS, RO only TDS before DI and final or RO/DI TDS.

When you start to see TDS in the treated water its usually the DI cartridge or resin that needs changing. I change my DI at anything other than 0.

Do not just change the DI though, you could be throwing good money after bad. The RO membrane could be bad and then you are using DI as a very expensive crutch to prop up a failing membrane and go though resin like crazy. Test the tap and RO TDS andsee how well your RO membarne is functioning. This can be very important and can save you a ton of money. Did you know that for every 2% you increase the RO membranes efficiency you DOUBLE the life of your DI resin? This can be big.

Keep the membrane well flushed at 4:1 waste ratio, confirm this with a measuring cup and clock or watch, and it should last for years if you also keep up with the 6 month prefilter and carbon block replacements and use high quality filters.

The prefilter and carbon have very little to absolutely no effect on final TDS, they trap the big stuff or suspended solids not small dissolved solids. Thats the work of the RO membarne and DI resin. Change the prefilter and carbon every 6 months and disinfect the system at that time regardless of usage or TDS readings. A TDS meter does not work for this. A pressure gauge is handy though as it can alert you to plugged or fouled filters with a pressure drop indication.