Is there something better than mixed bed DI resin? | BRStv Investigates

[Ryanbrs]

So, the results for cation and anion single media followed by a mixed bed are pretty dang impressive, but can we see if they outperform two mixed bed canisters? I would hate to add a third canister and buy additional media types to find no improvement.

Also, is this setup doable with the old blue mixed bed color changing DI resin or would I need to switch the 3rd canister to the purple mixed bed? I've got about 6 months worth of the blue stuff in my water shed and it's way too expensive to toss.

I would almost suggest not using color change at all on the third stage and just go off TDS but I know a lot of reefers won't want to do that. In a normal situation, it's better to have the dye (blue) in the anion resin because the anion has less capacity than the cation in a mixed bed. Most water supplies also have some amount of dissolved co2 which depletes the anion resin faster. End result is the anion resin in the mixed bed is very liky to get depleted first. You absolutely want the dye in resin which is going to deplete the fastest. This will give you an accurate depiction of when it has reached the end of its useful life, even if the cation still has capacity.

With the separated single bed design, general knowledge is sodium is the most common breakthrough issue and it is removed by the cation resin. All of the co2 has also been removed prior to the mixed bed so I think it is likely that the cation resin in the mixed bed will be depleted first. This is why the purple dyed cation resin might be the best option but I would monitor the TDS and make an informed decision based on your actual water.

 

[120reefkeeper]

One of the benefits a lot of reefers miss on this is when a single DI is 75% exhausted there is only 25% of the contact time. With your approach, you always have a full cartridge of contract time.

Exactly! I've learned some hard lessons not doing this. Great to hear that we are in agreement.

 

[chipmunkofdoom2]

Thanks for the info, BRS. I do have a question about how you got the numbers in the second column in your results chart.

The column for separate cation and anion stages lists the TDS as 2.18 PPM, or an EC of 0.57 uS/cm. I think one of these readings is incorrect, or there was a conversion error. To go from TDS to EC, you usually divide by the conversion factor (0.5 for NaCl). This produces a larger number in EC than TDS. To go from EC to TDS, you multiply by the conversion factor (0.5). This gives you a smaller number in TDS than EC. To convert 0.57 uS/cm to PPM TDS, you'd multiply by 0.5, which is about 0.285 PPM TDS, not 2.18 PPM TDS as shown on the table. To convert 2.18 PPM TDS to EC, you would divide by 0.5, which gives a result of 4.36 uS/cm, not 0.57 uS/cm as shown on the table.

To use another example, when I measure my tap water with my HM COM-100, it shows an EC of 396 uS/cm. When I switch the measurement to TDS PPM (NaCl), the reading shows as 190 PPM. 396 x 0.5 is about 190 PPM TDS. This math works the other way as well, 190 / 0.5 is about 396 uS/cm.

 

[revhtree]

Great read!

Hi Dr. @Randy Holmes-Farley , do you mind if I translate your post above? Reefers on my home country would love to ready and understand these valuable comments of yours. I'll include a link to the original post and credits back to you.

Anyway, thank you for taking time to spread the knowledge and make us understand a bit more of all chemistry involved in our hobby!

Absolutely fine with me if it's fine with Randy which I think it is! Maybe a ni e link back to this thread with it would be nice!

 

[Ryanbrs]

Thanks for the info, BRS. I do have a question about how you got the numbers in the second column in your results chart.

The separate cation and anion stages lists the TDS as 2.18 PPM, or an EC of 0.57 uS/cm. I think one of these readings is incorrect, or there was a conversion error. To go from TDS to EC, you usually divide by the conversion factor (0.5 for NaCl). This produces a larger number in EC than TDS. To go from EC to TDS, you multiply by the conversion factor (0.5). This gives you a smaller number in TDS than EC. To convert 0.57 uS/cm to PPM TDS, you'd multiply by 0.5, which is about 0.285 PPM TDS, not 2.18 PPM TDS as shown on the table. To convert 2.18 PPM TDS to EC, you would divide by 0.5, which gives a result of 4.36 uS/cm, not 0.57 uS/cm as shown on the table.

To use another example, when I measure my tap water with my HM COM-100, it shows an EC of 396 uS/cm. When I switch the measurement to TDS PPM (NaCl), the reading shows as 190 PPM. 396 x 0.5 is about 190 PPM TDS. This math works the other way as well, 190 / 0.5 is about 396 uS/cm.

Recording error is always possible and I noticed that as well. I am not sure on the exact math the Hach meter uses to convert TDS but it is not linear and the equation appears to change in different EC ranges. They are displayed at the same time on the same screen which makes recording error more difficult. Internally we focus on EC and don't spend much time considering the various conversions. In both cases, I believe the readings are higher than the mixed bed readings.

 

[Euler Kernighan]

I sent a report to the Reef2Reef owner to get his input.

Thank you!

 

[Euler Kernighan]

I sent a report to the Reef2Reef owner to get his input.

Absolutely fine with me if it's fine with Randy which I think it is! Maybe a ni e link back to this thread with it would be nice!

Absolutely! You guys rock! Thank you a lot!

 

[Randy Holmes-Farley]

Thank you!

I have no issue with translations. We just always need to check with the boss.

 

[Scott.h]

One of the benefits a lot of reefers miss on this is when a single DI is 75% exhausted there is only 25% of the contact time. With your approach, you always have a full cartridge of contract time.

What's the thoughts on getting zero tds well after the color change? How sensitive is the color change and what's really getting past being that it still reads zero with a pen style meter?

 

[Ryanbrs]

What's the thoughts on getting zero tds well after the color change? How sensitive is the color change and what's really getting past being that it still reads zero with a pen style meter?

The color change is based on the pH falling below ~10 and an indication that the anion portion of the resin is depleted. It is a fairly accurate indication but not in every case. As long as the TDS meter is accurate I would trust that first but if the DI resin is super old I would change it for peace of mind.

 

[Newb73]

The color change is based on the pH falling below ~10 and an indication that the anion portion of the resin is depleted. It is a fairly accurate indication but not in every case. As long as the TDS meter is accurate I would trust that first but if the DI resin is super old I would change it for peace of mind.

I did that early this year, trusting the tds meter over the color change and I think it may have been a mistake....the tds never rose much but I knew the resin had to be depleted even though my readings were good because I had ran so much through it.

Sure enough...the tank inhabitants improved greatly when I changed the resin.....leading me to think it had been suffering with the old....

 

[lactose]

What I wish existed (maybe it does?) is a TDS meter I can hook into my apex (or something) so I don't have to physically check in but can watch a trend or alert if it gets low. Then I could know 'automatically' when it gets too low between cartridges.

 

[Newb73]

What I wish existed (maybe it does?) is a TDS meter I can hook into my apex (or something) so I don't have to physically check in but can watch a trend or alert if it gets low. Then I could know 'automatically' when it gets too low between cartridges.

@Terrence

A TDS line from the RO unit directly to Apex...as an expansion kit?

I'd consider that.

The people that leave their lines pressurized all the time like the BRS tanks would definitely use it.

 

[Ryanbrs]

What I wish existed (maybe it does?) is a TDS meter I can hook into my apex (or something) so I don't have to physically check in but can watch a trend or alert if it gets low. Then I could know 'automatically' when it gets too low between cartridges.

@Terence , could you use the salinity probe for this? I know HM digital was considering a wireless version of their inline TDS meters. Apex ready version?

This seems like something pretty easy to do and shouldn't break the bank : )

 

[Terence]

Yes. It will measure TDS but in the new Apex it shows it always in PSU. You can still change the range though and calibrate with 447ms solution.

 

[PlanB]

I just changed out all my filters (sed, carbon, and resin), and I'm following the BRS custom DI with Single Bed Anion, followed by Mixed Bed (Purple). I have the BRS 6-stage water saver 150gal.

My question pertains to the TDS meter readings:
1st stage (after RO membranes) - 2ppm
2nd stage (after Single Bed Anion) - 6ppm
3rd stage (after Mixed Bed Purple) - 0ppm

Any idea why the TDS jumps from 2 to 6 ppm? It only occurred after I replaced the DI resin as described. Is this normal for this configuration?

 

[dragonfish]

FOLLOWING

 

[Scott.h]

Would the real Bobby Boucher please stand up.
I hear OCD people can make good reef keepers. I know in my head that I'm 106 TDS pre everything but... I'm all about creating problems to find solutions that I didn't have.

 

[Ryanbrs]

Yes. It will measure TDS but in the new Apex it shows it always in PSU. You can still change the range though and calibrate with 447ms solution.

Consider this a formal request for an apex RO/DI TDS/EC module : )

 

[Newb73]

Consider this a formal request for an apex RO/DI TDS/EC module : )

Hey i already requested that...lol