DI Cation Resin Low in / high out

[lapin]

Purchased new BRS resin for my 3 stage DI's.
The Cation (#1) is adding 2TDs to the water.
1 in 3 out.
This is something new. It did not do this on the last batch.
Anyone else have this happen?

 

[lapin]

Bumpin my own thread.

 

[MTBake]

I use the same resin setup. I have never checked the tds after just the first stage. Depending on what's in your water, that cation may not take out everything. The 2 stages work together. The cation is negatively charged and the anion is positively charged. Each resin will only take out the ions that are opposite of their respective charge. So, there is a chance that some ions can pass through the first stage. Really not sure why you're seeing a reading now versus last change though. Maybe something has changed with the source water?

How much water has passed through the resin since you changed it? Wondering if it could be manufacturing residue still rinsing off.

 

[Randy Holmes-Farley Verified Community Expert]

Purchased new BRS resin for my 3 stage DI's.
The Cation (#1) is adding 2TDs to the water.
1 in 3 out.
This is something new. It did not do this on the last batch.
Anyone else have this happen?

it should. An anion or cation only resin will raise tds as it passes through. Through both gives 0 ppm.

 

[Flippers4pups]

it should. An anion or cation only resin will raise tds as it passes through. Through both gives 0 ppm.

Is that why it's recommended to use a mix bed resin at the end? Makes sense.

 

[Randy Holmes-Farley Verified Community Expert]

A cation binding releases one or two H+ (Rarely 3) for every cation bound. H+ is by far the most conductive ion, so TDS rises and the pH drops.
The anion resin releases one or two OH- (rarely 3) for every anion bound. Hydroxide also conduct very well so the TDS and pH rise.

Then when those fluids combine, the H + and OH- combine exactly to make nonconductive H2O.

 

[JoshH]

My setups always done this and I just stopped following it as closely. Appreciate the actual science behind it though.

Thanks @Randy Holmes-Farley!

 

[lapin]

Kewl
Learn somepthin new every day
Thanks Randy

 

[Randy Holmes-Farley Verified Community Expert]

Kewl
Learn somepthin new every day
Thanks Randy

you’re welcome

Happy Reefing!

 

[mfinn]

I switched to the 3 part system last winter ( maybe earlier) and I decide to put a tds meter at each stage ( wish I hadn't) and that's the first thing noticed was a higher tds after the cation.
I kind of freaked out after spending the $. But after talking with BRS and using it for a while, I'm going much longer between changing out any of the resins.
With just a double mixed bed system, I was going through the di resin much faster than I had in previous years and decided to try this.

 

[lapin]

I go thru 100 gallons a week. Lets see how long 3 parts lasts. It only has to remove 1 tds

 

[NautiTang]

A cation binding releases one or two H+ (Rarely 3) for every cation bound. H+ is by far the most conductive ion, so TDS rises and the pH drops.
The anion resin releases one or two OH- (rarely 3) for every anion bound. Hydroxide also conduct very well so the TDS and pH rise.

Then when those fluids combine, the H + and OH- combine exactly to make nonconductive H2O.

This got me wondering at a potentially silly question. If you are having low pH problems could it be beneficial to have an anion stage last with no mixed bed?

 

[JMetaxas]

Had the same issue. I have a TDS meter after the RO (produces 3 ppm), then after the cation resin it was 17ppm. After my Anion resin, it is zero. I run a mixed bed after that too, getting a zero again.

When this first happened, I called BRS, but the guy who I spoke with didn't seem to understand, so I walked away more confused.

After doing a search here, I found my answer.

 

[Randy Holmes-Farley Verified Community Expert]

Glad to be helpful.

Happy Reefing!