7-stage RODI, 50% mixed bed left with 1-3 TDS.

[cloggins]

I wasn't sure where I should ask these questions. My RODI is BRS's 7-stage, 200 gpd setup. It has 3 resin chambers: cation, anion, and mixed-bed. The product water was 0 TDS when I first started using it. Lately, I've noticed it is starting to create product water w/ 1-3 TDS. The cation, and anion chambers haven't changed color much (if at all). The mixed-bed is about half depleted (according to the color).

So, would you change it out for fresh?
Is this expected behavior?
Is 1-3 TDS really that much of a problem?

Thanks all!

 

[dbjonesjr]

I change my mixed bed when it looks like that. That should fix the problem.

 

[Quietman]

I'd replace...you could have a bit of channeling going on not allowing you to use all the media. Not worth worrying about when you can replace cheaply.

Interesting it looks like top down depletion - did it start in the middle and work up? - mine always depletes bottom up.

Plus your anion and cation aren't depleting...usually it's them first. I think that's sodium...nothing wrong, I just find the different responses to RODI units fascinating.

 

[JS_racer]

#2 should go way before #3, something is wrong.
You are using the brs pro 1 and 2 then mixed correct?

 

[cloggins]

#2 should go way before #3, something is wrong.
You are using the brs pro 1 and 2 then mixed correct?

Yes. I order the replacement pack, and replace everything at once. This is the second time I've done a replacement.

 

[ca1ore]

I'd replace...you could have a bit of channeling going on not allowing you to use all the media. Not worth worrying about when you can replace cheaply.

Interesting it looks like top down depletion - did it start in the middle and work up? - mine always depletes bottom up.

Plus your anion and cation aren't depleting...usually it's them first. I think that's sodium...nothing wrong, I just find the different responses to RODI units fascinating.

Agree on channeling. The BRS resin holders should change color from the bottom up. That’s why it’s important (though not that easy) to make sure to pack the resin tightly. On my system, anion lasts about 5-600, mixed about double that ..... cation never depletes, or at least hasn’t yet.

 

[JS_racer]

Yes. I order the replacement pack, and replace everything at once. This is the second time I've done a replacement.

only need to replace what is used, that is part of the benefit of the 3 different resin pro series, #1 should look new, #2 should change color usually first, #3 should look new. after the initial pro purchased, i keep 1 or 2 #2 on hand.
could you have mixed #2 and #2 ??
has to be something, out of #2 should be zero tds or very close, #3 is just insurance for #1 and #2. if #3 smoked first, there definitely is an issue.

 

[Quietman]

#2 should go way before #3, something is wrong.
You are using the brs pro 1 and 2 then mixed correct?

Not necessarily...some molecules are neutral and need to go through cation/anion first before they can become an ion and get exchanged in the mixed. It's not common but it can occur.

 

[JS_racer]

Not necessarily...some molecules are neutral and need to go through cation/anion first before they can become an ion and get exchanged in the mixed. It's not common but it absolutely can occur.

The cation, and anion chambers haven't changed color much (if at all) #3 smoked, seems like its working as designed ??
or this goes to anything can happen ??

i would definitely touch base with BRS, see what they think .

 

[Quietman]

The cation, and anion chambers haven't changed color much (if at all) #3 smoked, seems like its working as designed ??
or this goes to anything can happen ??

i would definitely touch base with BRS, see what they think .

I think I did get this from BRS video - went and checked again - They mentioned sodium can do this specifically. I've seen some other stuff on ammonia at high pH as well that needs to go through one of the beds before getting picked up elsewhere.

Edit for clarification 1/13: I reviewed the video again to be specific they stated that the last mixed bed should be the purple cation indicating mixed bed as the most likely bleed through ion is sodium. It does not say that it will deplete faster than the single cation bed.

If the OP has water running through and it's indicating this way, then I would have to assume it's possible.

 

[I’m Batman]

This was the first search result in the query however I have the 3 stages for DI resin and was wondering, after the first two stages, do you use a cation or anion mixed bed For stage 3? My reef store runs out of stock and they only have one or the other sometimes.

In the winter our municipal water gets flushed with added silicates, so I always used the blue mixed bed but on BRS they show to use the purple mixed bed...

seems like if I have cation and anion for the first two stages, should I be choosing the mixed bed for my application or is it a rule of thumb to use the purple mixed bed in stage 3?

 

[JS_racer]

This was the first search result in the query however I have the 3 stages for DI resin and was wondering, after the first two stages, do you use a cation or anion mixed bed For stage 3? My reef store runs out of stock and they only have one or the other sometimes.

In the winter our municipal water gets flushed with added silicates, so I always used the blue mixed bed but on BRS they show to use the purple mixed bed...

seems like if I have cation and anion for the first two stages, should I be choosing the mixed bed for my application or is it a rule of thumb to use the purple mixed bed in stage 3?

I'm not sure if the difference is only in the color changing ability, and if the A or C causes it. i use a tds meter out of #2, and also out of #3. I think my resin is the regular stuff for the #3,
if i need to replace the #3, i would probably go with the pro #3, since BRS must know more than me, when they used that for the third stage. hope that makes sense.
(tds in, out of membrane, out of #2, out of #3 backlit meters. mainly watch out of #2 and membrane for tds bleed off)