Someone help me understand chloramines. And do I have some sort of magical carbon?

[BrettDS]

So according to my city water authority they are using chloramines in my water. I got my no name RODI filter almost 3 years ago and I have never replaced any of the filter media or membrane (other than the DI resin).

From what I've been reading recently it sounds like chloramines should burn through a carbon prefilter pretty quickly, but I've put thousands of gallons through this RODI unit and it still seems to be working great.

My tap water has a tds reading of about 280ppm. After the RO membrane it's about 20ppm and after the DI resin it's 0ppm.

I have test strips that measure free chlorine and total chlorine. When I measure my tap water I get a reading of 0ppm free and 1ppm total chlorine. When I measure my RO waste water I get a reading of 0ppm and 0ppm, which according to what I've read indicates that the carbon filter is properly removing the chloramines.

But from what I've read, three years and thousands of gallons should be well beyond the life of a standard carbon filter with chloramines.

Am I still in good shape here or should I be testing something else or should I just replace the carbon filter figuring that it's exhausted at this point?

Thanks much

 

[thegrun]

I do wonder if the chlorine test strip is not reading correctly. Here in SoCal when they started adding chloramine to our tap water it was definitely getting past my standard carbon filters in measurable quantities and I had to switch to chloramine carbon filters. Perhaps your city is only adding very small quantities of chloramines, but after 3 years I would think even chlorine would be getting past the old filters.

 

[JenkinsThePole]

Hmm 1ppm seems low for tap water. From what I could find most places use 4ppm.
Now I did find this on the interwebs:
https://chemistry.stackexchange.com/questions/26968/test-for-chlorine-and-chloramine-in-city-water-supply
The first answer could explain your situation. It sort of makes sense... Either that or you do have a magical filter.

 

[Zalick]

Your test strips are not measuring correctly. Your city water data sheet will tell you the ppm of chloramine. Generally it's around 2-3 I believe.

And your carbon would have been used up LONG ago. Chloramine requires long contact with carbon unlike chlorine. I burn through regular carbon in less than 500g total processed water and we have 2.4ppm if memory serves me right. I switched to chloramine specific and they last a lot longer.

I recently installed a big blue w 20inch chloramine andnthat will allow extended contact time and last for couplr years.

 

[BrettDS]

The test strips haven't expired and they do get a different reading on my tap water than the RO wastewater, but I do agree that the reading on the tap water seems low. Maybe I'll call lamotte on Monday and see what they think.

 

[SAT]

I found the following useful for understanding this problem:
https://www.wqpmag.com/catalytic-carbon-chloramine-removal