High Tide Aquatics

Challenges in removing chloramine in RODI setup

derek_SR said:
I am also using this - not really sure when to replace it, though. How are you testing for chloramines @Alexander1312 when I was on this road before, I could not really find a reliable test for chloramines - so I got the monster carbon filter and slapped it in my system upstream of the membranes and called it a day. I suspect it's working (just based on the fact that i change a lot of water and my corals mostly do well).
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Its not necessarily a tank topic, more an equipment concern - I am not seeing a positve test on my post DI water, only post RO.

I am using the test kit below, but the fact that an 11 USD test decides that I should be buy a 300 USD+ filter concerns me. So as mentioned above, if anyone knows a better chloramine test kit, I would be interested.

From what I understand, chloramine is a combination of chlorine and ammnonia. I wonder if the test is postive for ammonia, not so much for chlorine - since the catalytic carbon and 1 micron carbon which come before the RO could have already broken down the the chloramine and removed the chlorine but not the ammonia.

I need to look for an ammonia test kit and test for this as well.


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PjFish said:
Towards end of summer it’s common that some water agencies increase the chloramine levels to combat algae issues which may not reflect in their average data
Every few years depending on water levels around this time of year my tap water has a slight pond smell and taste lol since its primarily from reservoirs.
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The 2024 EBMUD report shows that chloramine levels can go up to 3.8 ppm.
 
Patio said:
I also use this. About time to buy a replacement cartridge. Do you know where to find them?
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Apparently the cartridge can process 75,000 gallons of water so it will last a very long time! Replacement filters can be purchased from online water filtration sites for $256 or so. This is the search term you can use in Google: Pentek CRFC20-BB cartridge
 
Some more water chemistry details re chloramine levels.

I am still working on a fix with Chris / Airwaterice.com.

Relationship between pH and chloramine levels

Chloramine (a compound of chlorine and ammonia) stability and presence are influenced by pH because the ratio of ammonia (NH₃) to ammonium (NH₄⁺) changes as pH varies. According to the FAQ content, when pH is below 7, over 95% of ammonia exists in the ammonium (NH₄⁺) form, which is easier for filtration systems—particularly reverse osmosis membranes—to remove effectively (showing >98% rejection). However, as pH increases, the equilibrium shifts toward un-ionized ammonia (NH₃), which is much less rejectable by RO membranes. This same chemistry affects chloramines because they derive from ammonia bound to chlorine.[airwaterice]

At higher pH levels, chloramine formation becomes more stable, meaning residual chloramine levels in water supplies tend to remain persistent. This increases the need for catalytic carbon filtration, which the FAQ specifically recommends “for chloramine removal” due to its superior oxidation capability. Therefore, high-pH water maintains chloramine longer, making it harder to remove through standard carbon filters or RO membranes alone.
 
Slingfox said:
Apparently the cartridge can process 75,000 gallons of water so it will last a very long time! Replacement filters can be purchased from online water filtration sites for $256 or so. This is the search term you can use in Google: Pentek CRFC20-BB cartridge
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92.00 for ten inch or 174.00 for 20 inch for the replacement cartridges
256.00 was probably for the whole housing
 
Adauqua said:
@Alexander1312 - if you open for other cheap solution, you can try vitamin C powder (ascorbic acid powder good grade - Amazon) which can effectively/instantly treat chloramine and chlorine. For about 6 months, I have used 500mg to treat 5gl RODI. Extra/left-over vitamin C will be coral food. I still replace my cartridges every 6-9 months.
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Wow, this is out of the box. Is this because I assume it significantly lowers PH, which makes it much easier for carbon to remove chloramine. Interesting.
 
PjFish said:
Nice ! Never heard of that before
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Alexander1312 said:
Wow, this is out of the box. Is this because I assume it significantly lowers PH, which makes it much easier for carbon to remove chloramine. Interesting.
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Dong Zou talked about it in one of the youtube episode about input/output in reef tank. I forget all about chemistry, the below answer is from AI

How vitamin C neutralizes chloramine
The chemical process, a redox (reduction-oxidation) reaction, involves vitamin C donating electrons to the chloramine
  1. Reaction:Ascorbic acid (C6H8O6) reacts with chloramine (NH2Cl).
  2. Products: The reaction produces dehydroascorbic acid, hydrochloric acid (HCl), and water.
  3. Result: The chloramine is broken down into chloride, a normal component of drinking water, and trace amounts of ammonia. The change in pH is typically minimal unless a very high dose of vitamin C is used
 
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