RO unit: DI resin depletes quickly

[Mr31415]

Just got my pressure gauge - it reads 55psi to the intake of the membrane so that checks out. I have new resin in and that seems to behave differently. I am monitoring it…

 

[Paul B]

I can't tell from the picture but is the water going from those three canisters into the RO membrane and then to the DI resins?

 

[laverda]

Like Kharmaguru said get an inline tds meter nd measure before the DI and after. If your ro water is 20 and above before your DI cartridge, your DI will be depleted quickly.

My TDS is well below 20 going into the DI and I csn probably only make 300 callons out of a cartridge. I typicaly make 40-60 gallons at a time.

 

[griss]

Just got my pressure gauge - it reads 55psi to the intake of the membrane so that checks out. I have new resin in and that seems to behave differently. I am monitoring it…

I run my pressure (using a booster pump) between 70-80 psi. Per Bulk Reef Supply "The ideal operating pressure is 75 - 85 PSI for many common RO membranes." So, if you have the funds and ability to add a booster pump, you will likely increase the life of your DI cartridge.

Also, your system utilizes a mixed bed resin. Mixed bed resins consist of a mixture of Anion and Cation resins. Depending what is in your source water one of those resins may deplete faster than the other causing the entire cartridge needing to be replaced. I can't remember off the top of my head but, one of my resins depletes quite a bit faster than the other.

That's why a lot of us run three separate cartridges of DI...Cation, followed by Anion and finally a Mixed Bed. With this setup, you can replace each type of resin individually. The reason we run a mixed bed at the end is, in the event the Cation or Anion are depleted before we notice, the mixed bed will remove any TDS escaping those.

Like Kharmaguru said get an inline tds meter nd measure before the DI and after. If your ro water is 20 and above before your DI cartridge, your DI will be depleted quickly.

Yep, I can't remember what my source water TDS is at the moment. But, turning on the system on to flush the membrane for TDS creep, it can range anywhere from 20-90 TDS depending on how long the system has sat idle. After flushing the membrane, the TDS (out of the membrane) lowers to 6-7. Then, it's zero after the three DI cartridges.

 

[five.five-six]

Just got my pressure gauge - it reads 55psi to the intake of the membrane so that checks out. I have new resin in and that seems to behave differently. I am monitoring it…

55 PSI is a bit low but still functional.

Do you know what your TDS is out of the membrane?


A trick I use is I have 2 stages of DI resin. A first stage and then a polish stage. Once my TDS our of the polish stage reads 1PPM, it gets moved to the 1st position and the cartridge in the first position gets repacked and put in the polish position. I estimate that I get 2-3X the life out of my resin this way.

 

[Mr31415]

I can't tell from the picture but is the water going from those three canisters into the RO membrane and then to the DI resins?

Yes