Are you throwing away perfectly good DI Resin?

So your DI resin hits the dreaded 1ppm reading.. For most reefers, this is likely something they see every 6 to 12 months. They then dig through their supply closet or garage for the bag of spare DI resin to empty and refill their cartridge or order a replacement from their favorite site. You folks can likely ignore this thread!!! For others, this activity is every month or two... So why do we throw away DI resin that is capturing all but 1ppm TDS?

DI Resin.jpg

About a year and a half ago, I moved into a home on a well. When I went to fill my tank for the first time, I went through a cartridge of DI resin in about 60g of RODI... I went through all the tests imaginable, including a CO2 test, and it came back slightly elevated, but overall normal. My well had high iron, removed via an iron removal system utilizing GAC and injected fresh air that got flushed every night and a water softener. I replaced the RO membrane, thinking mine could be compromised.. no effect.

At the end of the day I settled for the fact that my TDS coming in was well over 700+ (sometimes over 800) but always settled at 15 TDS after the RO membrane.

I finally caught on to the fact that my RO membrane put out 15 TDS but I was throwing away DI resin that was still effective at removing 14 TDS.. So I asked myself why? Then shortly after, I ordered a second DI canister. WOW did my resin last a lot longer. Now I was using my existing DI resin more effectively by further reducing the "old DI resin" to remove a majority of the impurities.

Finally, when the old resin made it to 4ppm, I eventually hit 1ppm in the newer DI resin. Swapped the cartidges between the new and old, and the old one was dumped and replaced with fresh resin.

RO -> DI
15tds 0tds
15 tds 1 tds then replace DI resin that was only utilized to 1ppm

RO -> DI-1 -> DI-2
15 tds 1 tds 0 tds
15 tds 4 tds 0 tds
15 tds 4 tds 1 tds then swap DI-2 to D1-1 and replace DI-2 with new DI resin

I then found a pre-owned DI canister being sold locally and decided a third couldn't hurt.

RO -> DI-1 -> DI-2 -> DI-3
15 tds 4 tds 1 tds 0 tds

This is as far as I have gotten with the addition of the third canister. Time will tell how effective this will be.

For those of you throwing away a lot of DI resin, this may be your answer.

  • Non-branded 5 stage RODI
  • Two additional DI canisters run in series
  • BRS Bulk non-color changing DI resin
  • CDP-8800 Pressure Booster
Here are the latest results ICP results for my RODI





About author
Jon is a hobbyist through and through tacking DIY home remodeling projects to tinkering with all types of technology creating a fantastic foundation for the Aquarium addiction.

He has been keeping aquariums for over a decade of which saltwater has been a key focus since 2012.

Article information

Last update
4.90 star(s) 10 ratings

More in General Saltwater Aquarium

More from ihavecrabs

Share this article

Control EcoTech, Reef Octopus, Maxspect, & More!
Red color accents to match all your OCTO gear!