Chloramine Monster

[Randy Holmes-Farley]

I believe to answer your original question, no standard carbon filters are not as effective at chloramines specifically, catalytic carbon breaks down chloramines like GAC works on chlorine. Standard GAC filters need a very long dwell time to get to chloramines, and we cannot guarantee that with typical usage. I assume that is what is in the product you mention but I am not certain never used it. I use Matrikx in a standard 10" filter. So yes, this in front of your DI resin I think would work. I use it with freshwater on an auto water change system and it gets the chloramines the standard whole house carbon I use lets by. Most of the year it is not an issue, but it seems like whenever there is an issue with a well my city dumps in chloramines and we learn about it after the fact. No bueno to not catch those.

Well, it worked perfectly well for me and many others.

 

[Submerge]

Well, it worked perfectly well for me and many others.

Thats awesome it worked for you. Its pretty application dependent tho. If you have the dwell time in GAC and low overall chloramines, I'm sure its now ready for the RO membrane and DI resin to mop up whatever remains. But that's not the question being asked here.

If I am wrong about the catalytic carbon, please point me to a link to get educated.

 

[ReefHunter006]

Here is the latest test after the carbon block. South Bay Area has been using chloramines since 2024. Looks like zero to me. Let me know if anyone disagrees.

Additionally I changed out the membranes today since I do that every two years anyway. One looks slightly worse than the other. Not sure what a degraded membrane looks like.

 

[Submerge]

Here is the latest test after the carbon block. South Bay Area has been using chloramines since 2024. Looks like zero to me. Let me know if anyone disagrees.

Additionally I changed out the membranes today since I do that every two years anyway. One looks slightly worse than the other. Not sure what a degraded membrane looks like.

Your test detects total chlorine in tap correctly? If yes then sounds like you have it figured out.

I get no where near 2 years out of my membranes. But they get used a fair amount. More about gallons and source quality than length of time so my experience will be different than yours.

 

[ReefHunter006]

Your test detects total chlorine in tap correctly? If yes then sounds like you have it figured out.

I get no where near 2 years out of my membranes. But they get used a fair amount. More about gallons and source quality than length of time so my experience will be different than yours.

I run about 300 gallons a month through it but inbound tds is only in the 50s.

 

[Randy Holmes-Farley]

Thats awesome it worked for you. Its pretty application dependent tho. If you have the dwell time in GAC and low overall chloramines, I'm sure its now ready for the RO membrane and DI resin to mop up whatever remains. But that's not the question being asked here.

If I am wrong about the catalytic carbon, please point me to a link to get educated.

Just to clarify, this is the testing we did on numerous systems that strongly supports the idea that I espouse that folks should not jump to expensive alternatives without seeing if cheaper normal carbon blocks are adequate. Of course, if they are not adequate, then more expensive options are justified.

Chloramine and the Reef Aquarium -

Removing Chloramine With Activated Carbon: Does it Really Work?

There has been much debate over whether commercial RO/DI systems used by aquarists are actually removing chloramine in adequate quantity. The concern is not whether they can theoretically do so, but whether the actual units allow sufficient contact time between the water and the activated carbon for the units to do an adequate job.

I have been using a Spectrapure RO/DI system (CSP25DI) for years, and my water does contain chloramine, so naturally I was interested to know if it was up to the task. In discussing the issue with Charles Mitsis, President of Spectrapure, he said that my water was among the most difficult to successfully remove chloramine from because the pH was high, and he was not sure that the unit was adequate. The reasons for being concerned were that:

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1.​	Monochloramine is the most difficult of the three chloramine species to remove because it is small (allowing it to pass through a reverse osmosis membrane).
2.​	Monochloramine is the most chemically stable of the chloramine species, so is the hardest to break down (as on activated carbon).
3.​	Monochloramine predominates over the other forms in tap water at pH above 7 (dichloramine predominates at pH 4-7).
4.​	The pores of the activated carbon may become plugged with sediment over time, reducing the effectiveness of the carbon at breaking apart chloramine.
5.​	At high pH, the pores of the RO membrane can swell, resulting in poorer rejection of impurities.

With this as the backdrop, I set about organizing a round of testing by aquarists to see if their commercially-available systems were adequately removing chloramine.

First, I selected a single, high quality test method for participants to use: the Hach CN-70 kit described above. I then asked aquarists to test several things:

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1.​	The free and total chlorine in their tap water after letting it run for a while.
2.​	The free and total chlorine in their RO reject water.
3.​	The free and total chlorine in their finished RO/DI water.
4.​	The pH of the tap water.

In my case, for example, I had the following results:

Tap water:
pH ~9
Total Chlorine: 0.4-0.5 ppm one day, 0.08 ppm on a second day.
Free chlorine: <0.01 ppm (effectively all of the total chlorine was chloramine)

RO Reject water:
Total Chlorine: 0.02 ppm
Free chlorine: <0.01 ppm

Final RO/DI water:
Total Chlorine: <0.01 ppm

Consequently, within the capabilities of the Hach test kit (0.01 ppm), there is no chloramine getting through the system. A small amount does appear to get past the carbon to the RO waste water, but it does not get through the RO membrane and DI resin.

A similar set of data (more or less complete) was collected from about 20 aquarists in different parts of the country. These included systems that were stated to have a capacity of 25-100 gallons per day, the higher volume systems being especially interesting because the contact time with the carbon might be shorter. All but one had similar results to those reported here. The anomalous report produced the following results:

Tap Water:
pH 8.2
Total Chlorine: >3.5 ppm
Free Chlorine: >3.5 ppm

Filtered Tap Water: (single cartridge under sink, cold water side)
Total Chlorine: 0.7 ppm
Free Chlorine: 0.38 ppm

RO water: (11 month old cartridges)
Total Chlorine: 0.16 ppm
Free Chlorine: 0.06 ppm

RO/DI water: (11 month old cartridges)
Total Chlorine: 0.04 ppm
Free Chlorine: 0.02 ppm

RO/DI water: (Fresh cartridges)
Total Chlorine: <0.01 ppm
Free Chlorine: <0.01 ppm

In short, his tap water chloramine (and chlorine) levels were quite high. His old carbon and sediment cartridges were not quite up to the task, but when replaced, were adequate to remove all of the chloramine. Note that the 11 month old cartridges were still producing 0-1 ppm TDS RO/DI water.

Lessons Learned and Suggestions:

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1.​	Most RO/DI systems seem capable of removing chloramine adequately for aquarists.
2.​	The carbon cartridge may become less useful over time, and it is possible that the chloramine removal effectiveness of a system may be lost before the DI appears to need changing.
3.​	Cheap sediment cartridges may expose the carbon cartridge to unnecessary fouling, which may permit chloramine to pass through the system. Cartridges should be replaced as soon as the pressure drops significantly, even if RO/DI water is still being produced at a reasonable rate or purity as measured by total dissolved solids.
4.​	Testing for chlorine and chloramine is easy, so any concern is easily reconciled.
5.​	One Hach kit provides several dozen test results. Our local Boston Club bought some kits and had a "water testing day." The kits can also become part of the "library" of a local club for aquarists to use once in a while to see if their systems are functioning. That way, the cost to each aquarist is minimal.

 

[ReefHunter006]

Would the cation or anion resin remove residual chlorine/chloramines? I go though 3x the amount of anion versus cation.

 

[Randy Holmes-Farley]

Would the cation or anion resin remove residual chlorine/chloramines? I go though 3x the amount of anion versus cation.

That effect would generally be from CO2 in the water. While hypochlorite that got through an ro membrane will bind to the anion resin, the balancing counterion (such as sodium) that must be there in equal amounts will bind to the cation resin. The amount of chloramine that is not broken apart that would bind to a di resin is small.

 

[ReefHunter006]

That effect would generally be from CO2 in the water. While hypochlorite that got through an ro membrane will bind to the anion resin, the balancing counterion (such as sodium) that must be there in equal amounts will bind to the cation resin. The amount of chloramine that is not broken apart that would bind to a di resin is small.

Pesky CO2