Problem with Custom DI Setup

[redfishbluefish]

This has me absolutely and totally perplexed!!!


I regenerate my DI resin….been doing it for some time. This is not the issue.

The biggest PIA is first separating the two resins to clean them up.


So I was fortunate to come upon an old RO setup with two canisters.

I figured I’d remove the RO membrane and polishing carbon filter and turn it into a DI unit with separate “bedsâ€â€¦â€¦.The cationic resin in one, and the anionic resin in the other. This way, when I go to regenerate, no first step of separating the two resins. I purchased two DI canisters from BRS and had plenty of resin to get this thing going.

I will tell you that in the process of taking off the RO stuff, I noticed the two canisters, that are labeled “IN†and “OUT,†had both “OUTs†connected. I flipped this one canister around so that the “OUT†of the first canister entered the “IN†of the second canister.


So here is my problem….I now have attempted this three times….I can’t get down to zero TDS. My most recent attempt was letting the unit run for six hours, and after six hours, I can only match the TDS of the incoming water. The same result for all three separate times I’ve tried this.

(The number on the left is TDS before the DI resin, the number of the right is after the DI resin.)

Now, I take this same resin and mix it up and put in it a single canister and I’m now back to zero TDS within a minute of starting the water flowing.

What’s going on???

 

[Eienna]

Did you let the membrane dry off at all? That will ruin it. Also, I notice you don't appear to have a sediment or carbon filter on there?

 

[redfishbluefish]

Did you let the membrane dry off at all? That will ruin it. Also, I notice you don't appear to have a sediment or carbon filter on there?

I apologize, I wasn’t totally clear.

The RO membrane isn’t in play here.


I still have a four stage (some say five), RO unit. What I’m attempting to switch out is a single canister mixed bed resin DI unit, with a separate bed (two canister) unit, where the cationic resin is in one canister, and the anionic resin is in the other (Similar to a Kati/Ani System.)



In this picture you can see my RO unit, and below, the original mixed bed canister (right) and “new” separate bed (on the left). (In between is the drain to my washing machine.)

 

[Eienna]

Very peculiar. Maybe it's not packed tightly enough in the double canisters?

 

[redfishbluefish]

Very peculiar. Maybe it's not packed tightly enough in the double canisters?

No different from when I pack the mixed bed.

 

[redfishbluefish]

When I was typing the OP, I came to the part about the IN and OUT of the two canisters and thought, “What the hoot, let me flip them back around and see what that does.” I wasn’t overly optimistic, but maybe these RO folks know something I don’t know. By the way, the IN side allows water to enter on the outside of the inner canister, and exit by going up the inner canister….and vice versa.

No dice! I only let it run for five minutes, but the outflow was now greater than the in flow.