Cali Kid Corals

Big Fan of Separate DI Resins

MolaMola

MolaMola

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With expertise of forum posts and @Coral reefer, I just upgraded my RODI to include a booster pump, two RO membranes, and separate DI resins. I am already blown away! I have been burning through mixed bed resin like you wouldn't believe and lately not testing/changing resin and using product water with too high TDS. But today... excellent water pressure, fast production, greatly reduced wastewater, and check this out... TDS entering first resin (cation) is 18. It leaves at ZERO. Shocked. This explains my fast depletion of mixed bed and why it did not look depleted to me. Half of it was along for the ride. It will be interesting to see how it goes. I have different water at my home, so was surprised to see the tank location's Contra Costa WD water has TDS of 330.
 
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As soon as I burn through the mixed resin that came with the canister, I am going to 2x anion + cation + mixed too! Makes way more sense. We do have lots of chloramine here, so I get using 2x carbons, or one chlorine block and one chloramine.

Edit: we have more anions I guess, so 2x anions
 
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Well, now I'm confused. TDS entering cation resin is 14 and reads 0 afterward, before entering anion resin. But I see this - anion is changing color. Not sure what is going on. Guess I should check the built-in sensors in case they are off.
resinQ.JPG
 
Also, the whole point of doing the separate resins is that they will typically be used up at different rates, so absolutely expect one resin to get used up faster than the other considering they're the same volume.

Mixed bed resins do take this into account and have a particular ratio of cation/anion (couldn't tell you off the top of my head what it is), but if your water differs from what the resin manufacturers think is in your water you may end up "wasting" some resin when you change it out. So leaving it as the last line of defense in a case like this helps you waste slower :)
 
Thanks for the info. All this time I assumed TDS told me if anything was in the water that would be detrimental to a tank. Since it went from 14 to 0 I thought the cation resin was doing all the work, but its color has hardly changed at all. The anion resin is changing much faster despite no TDS change, so I guess it is grabbing chloride and sulfate. Water quality report did not give much info and was two years old.
Just when I think I understand something in reefing...
 
Hi Maureen,

I believe the sensor on the anion is on the output side. My anion looks like it will last for some time.
 
Hey Maureen, your 1st sensor is before the 3 DI canisters, your 2nd sensor is after both the cation and the anion canisters but before the mixed bed. I tried to markup your pic to demonstrate:

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So with this placement, your TDS readings make sense!
 
Doh! I was mistaken in where my TDS reading was being taken. Thanks to @Yippee and @JVU for catching it. No mystery at all and I am using up the anion, not the cation resin. Lucky I did not stock up on cation yet. And I am so loving the fast rate of watermaking!
 
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