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RO unit for water with chloramines

Ben Rhau

Apisto Club
5 Year Member
Messages
650
Location
San Francisco
Hi all,

I'm in the market for an RO unit, and my tap water is very soft, but contains chloramines and NaOH. According the literature, most carbon blocks do not efficiently remove chloramine, and the vendors recommend a 5 or 6 stage RO/DI to effectively remove chloramine. My question: Is it worth adding the two additional stages to remove chloramine, or should I just get a 3-stage RO and add Prime to the output?

Thanks
 

Ben Rhau

Apisto Club
5 Year Member
Messages
650
Location
San Francisco
One thing I'm reading is that, unless removed first, chloramines will degrade the RO membrane. The proposed mechanism is that, at high pH, the chloramine dissociates into ammonium and hypochlorite ions, and it's the ammonium ions that deteriorate the membrane. Has anyone experienced this?
 

MacZ

Well-Known Member
Messages
3,721
Location
Germany
Hi all,

I'm in the market for an RO unit, and my tap water is very soft, but contains chloramines and NaOH. According the literature, most carbon blocks do not efficiently remove chloramine, and the vendors recommend a 5 or 6 stage RO/DI to effectively remove chloramine. My question: Is it worth adding the two additional stages to remove chloramine, or should I just get a 3-stage RO and add Prime to the output?

Thanks
I live in a country where chlorine and chloramine are removed at the water plant before sending the drinking water into the public system, so I don't have any in my tap, but I have helped dozens of people now getting their units set up in countries where the stuff is in the water system, all with a 3 stage (carbon, sediment, membrane) units have reported trouble free removal and tested no chloramine nor chlorine in the permeate.

One thing I'm reading is that, unless removed first, chloramines will degrade the RO membrane. The proposed mechanism is that, at high pH, the chloramine dissociates into ammonium and hypochlorite ions, and it's the ammonium ions that deteriorate the membrane. Has anyone experienced this?
As far as I know any ions with a higher reactivity (or very high concentration) have deteriorating influence on the membrane and it is not like the membrane is going to be worn out very quickly. But it raises waste water amounts significantly and reduces the lifetime of the membrane by some months.
 

MacZ

Well-Known Member
Messages
3,721
Location
Germany
Ok. Thanks for the additional material. I can link people to this in the future. For myself it doesn't change anything, luckily.
 

Mike Wise

Moderator
Staff member
5 Year Member
Messages
11,526
Location
Denver, Colorado, U.S.A.
My tap water contains chloramines and Na(OH) too. I just add a dechlorinator to the R/O water as I add it to the tank (directly into the tank actually). I've been doing this for years without problems.
 

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