Does a RO, filter out chloramines?

[hillegom]

I know the carbon in a RO filter will take out the chlorine that is in the water, but without a DI, will the chloramines (NH2Cl) also be taken out?
I have a RO/DI but my brother who has fresh water fish, only has an RO.

Sodium thiosulfate (Na2S2O3) will dechorinate the water, but it leaves the ammonia behind. I do not want that.

Any chemists feel like chiming in?

I guess that you could always buy a complete conditioner, but I was looking for something more DIY

Thanks

[mark]

sure hope so as that's all I use.

[mike31154]

Not a chemist, but if not mistaken, most RO systems designed to handle chloramines have an extra carbon stage before the membrane. Both chlorine and chloramine will destroy your membrane in short order, the DI has nothing to do with removing either since it's downstream of the RO membrane. Don't know if there's anything special about the extra carbon stage. I believe my BWI system is rated for chloramines since it has the extra carbon stage. So my config is 1 micron poly pre-filter, re-fillable carbon stage, 0.5 micron 'chlorine guzzler' carbon block, RO and finally DI. In my case it doesn't really matter since I know that my source water is treated with chlorine only, not chloramine. I've been considering dumping the first carbon stage and replacing it with another poly pre-filter, say one 5 micron, then a 1 micron, then the carbon block.

[Doug]

I would think Mark & Mike are on the money. Does carbon not remove them? I run a 5m, 1m, then my carbon filter before the membrane and also a post carbon. I also plan on switching the first stage 5m for a 5m carbon impregnated filter.

My membrane made 4 yrs. so must be doing something correct.

[mike31154]

This thread got me wanting more info on the subject of chloramines. Here's a link to a fairly good read. No idea how reliable or factual, but seems legit (Citizens Concerned About Chloramine, San Fran Bay Area, Cali) . Scary stuff actually, both chlorine and chloramines. Chlorine does seem to at least have the advantage that it will dissipate on its own if water is left standing in an open container for a sufficient amount of time.

According to one quote in the article, the RO membrane does actually remove one component of chloramine after the carbon stage.... and a DI filter would work as well, part of it anyhow. I think most of us use mixed bed DI media, cations and anions. The cation part will remove ammonia.

"To remove chloramine, an extensive carbon filter (to remove the chlorine part of the chloramine molecule) followed by a reverse osmosis or cation filter (to remove the ammonia) is necessary."

http://www.chloramine.org/chloraminefacts.htm

[hillegom]

Mike31154 that is a very good and scary article about chloramines. I didn't know they were that bad.
If I remember correctly, I think I read, a few years ago that Surrey was going to use chloramines. or was it the GVRD?