Does Reverse Osmosis water contain any ions at all? - Home Brew Forums
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Old 05-30-2010, 12:08 AM   #1
hokenfloken
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Feb 2009
Charlotte, Michigan
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Greetings! I've been searching the forum for awhile now and I cannot find any definitive answer to this question.

I currently build my water from distilled water and brewing salts. I would like to start using RO water due to the lower cost.

Can I expect RO water to be nearly free of salt ions?

Any experienced advice would be greatly appreciated. Thank you very much.



 
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Old 05-30-2010, 12:30 AM   #2
Special Hops
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Kanatenah
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http://en.wikipedia.org/wiki/Reverse_osmosis



 
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Old 05-30-2010, 12:37 AM   #3
hokenfloken
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Feb 2009
Charlotte, Michigan
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Thanks for the wikipedia link, although I have read it already. I guess my question whether or not any of the salt ions are smaller than 0.1 nm. If they are larger, they will be filtered out. If not, they will pass though, or at least that's my interpretation. If RO water is essentially free of ions then what is the point of distilled water? Thanks.

 
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Old 05-30-2010, 11:01 AM   #4
artbrau
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I believe distillation and RO are two different processes that get you to the same place.

 
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Old 05-30-2010, 01:02 PM   #5
remilard
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Nov 2008
Kansas City
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Quote:
Originally Posted by hokenfloken View Post
Thanks for the wikipedia link, although I have read it already. I guess my question whether or not any of the salt ions are smaller than 0.1 nm. If they are larger, they will be filtered out. If not, they will pass though, or at least that's my interpretation. If RO water is essentially free of ions then what is the point of distilled water? Thanks.
RO doesn't exclude particles solely on the basis of size, so your interpretation isn't quite correct.

The answer to your question is that the water will not be ion free, there will be lower ion content than there was before, it will probably be very low (single digits ppm for each ion), and it is impossible to predict exactly what it will be.

 
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Old 05-30-2010, 02:52 PM   #6
Hoppocrates
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May 2010
Coralville, IA
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A member of my home brew club sent the supermarket RO refill station water to the lab. It was surprisingly incredibly efficient and nearly distilled. You can see the results at the bottom of this page:

http://www.thirstyhomebrew.org/

 
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Old 05-30-2010, 06:00 PM   #7
bad coffee
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IF you're using RO-DI (DeIonized) water it should be 0 PPM. If it's just RO, then it will depend on the membrane.

(From my aquarium knowledge)
A 100GPD (Gallon per day) filter has a 90% rejection rate.
A 75GPD has a 97% rejection rate.

So depending on the membrane, you might be getting really good water or just good water. YMMV.

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Old 05-30-2010, 10:03 PM   #8
GreenMonti
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Nov 2009
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I have a RO/DI unit for my reef aquarium. Every time I fire it up I hit the TDS meter to check my incoming and outgoing TDS rate. Since day one I get 0 PPM on the outgoing.

The above post about the membrane is correct. I also believe the quality of the membrane has to do with its rejection rate.



 
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