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Topic: Reverse osmosis water leaching copper from brass?  (Read 17322 times)

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UptheDownstair

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Reverse osmosis water leaching copper from brass?
« on: May 16, 2005, 11:45:53 PM »
Hi everybody! (Hi Dr. Nick!  ;) )

This is sure to be an unusual queary because Im not working on chemistry homework  ::)  Im actually a poison dart frog hobbiest and I have a living vivarium with an automated misting system.  View pictures here---> http://imageevent.com/audiomaster/tincvivarium  

I use reverse osmosis water for the misting system and have nozzles made of brass, as well as small sections of bent brass tubing to direct the spray of each misting nozzle.  It has reciently come to my attention while participating in this thread at www.dendroboard.com that reverse osmosis water can actually break down brass and leach copper out of it :o  This is bad because as most of you probably know, copper is an active ingredient in many plant killers!  

First off, I obviously dont want to kill all the plants in my tank, but I also dont want to have to replace every misting nozzle with plastic if I dont have to.  Could I add a water treatment to the misting water which is labeled to "detoxify up to 1.0ppm of copper per dose" thereby removing the copper before it can harm the plants?  

Is it true that water which has been completely stripped of all it's minerals and trace elements becomes more agressive because pure H2O naturally wants to mix/bond with embeded or free-floating minerals and trace elements?  Would that explain why pure H2O passing over brass, or any other material for that matter, would want to leach metals (such as copper) out of them?  

Thanks for any help or insight to my problem, I hope it's not too out-there for this kind of forum  :-\  ;D

-David

Offline eugenedakin

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Re:Reverse osmosis water leaching copper from brass?
« Reply #1 on: May 17, 2005, 12:29:43 AM »
Hello David,

This topic is a double-edged sword that has two-tales ... I'll explain my interpretation of the two areas, and let you judge (or experiment) for yourself.

On one hand, many fellow corrosion collegues have proven that reverse osmosis water (less than 0.01 Total Dissolved Solids, ppmv) is almost non-corrosive because of the very low TDS value (there are virtually no chlorides/sulphates etc which provide conductivity to promote corrosion).  On the other hand, the biologist in me says to never use reverse osmosis water on any life form.  I do not remember the original surgeon, but the story goes something like this.  A surgeon who performed operations removing problems from various internal organs originally used reverse osmosis since it is pure (this is absolutely true) and contained little to no infectious agents (microorganisms).  The problem that did occur, was that when reverse osmosis water was being used on the tissues, the osmotic pressure would increase (regular tissue osmosis) causing the tissue that was being operated on, to swell and burst.  The reverse osmosis water would be absorbed by the cells and become so large that the membrane would rupture.  Once the reverse osmosis water was determined to be the problem, inorganic salts were added in small concentration to prevent cell burting from occuring during operations.  

Similiarly, this may occur to your plant, you may be bursting the cell tissues.  Granted, cellulose fibers (in plants) are usually much stronger than lipid layers (in humans), and water is no longer 'reverse osmosis' water once it touches the soil and absorbs nutrients/salts/etc.

Reverse osmosis water tends to have a lower pH (approximately 6 or so), and pH values below 7.5 tend to be more corrosive.


On the other hand, the regular salt concentration of tap water (lets say 140 ppmv TDS) contains many salts including sodium chloride and chlorine gas.  This salt content increases the liquids conductivity and forms a conductive cell (similiar to a battery in your car, but only producing very small voltages and current) that cause the different metals in brass to corrode.  In industrial water plants, calcium carbonate is added to form a hard protective coating to prevent the iron piping from direct contact with the water and salts, thus lowering corrosion.  At this concentration of TDS, most cell membranes tend to remain stable, and not burst in the situation previously described with reverse osmosis water.  Tap water usually has a pH between 7.5 and 8.0 (less corrosive), but does have about 2 ppm of free chlorine gas, which is quite harmful to microorganisms, which help create good soil for plants.

After all of this, I would recommend changing to plastic misting nozzles.
  ;)


I hope this helps,

Eugene Dakin Ph.D., P.Chem.
There are 10 kinds of people in this world: Those who understand binary, and those that do not.

UptheDownstair

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Re:Reverse osmosis water leaching copper from brass?
« Reply #2 on: May 17, 2005, 12:54:56 AM »
Thank you for the quick and informative reply!  ;D  I guess Ill be buying some plastic nozzles then ::)  

*edit*
About not using RO water on any life form: Isnt biologically correct rain water 100% pure H2O with no disolved solids?  The same as distilled or RO water?  Im just thinking of the safety of my frogs now because Im misting them 5 times a day with pure RO water and I surely dont want their skin cells to rupture! :o  But if this was the case, wouldnt there be the same risk whenever there was a heavy rainfall in the jungle?  If you think I should add something to my misting water what would you suggest?  I dont want to have any calcium or mineral stains on the aquarium glass if it's avoidable.  Thanks again!

-David

« Last Edit: May 17, 2005, 01:13:01 AM by UptheDownstair »

Offline xiankai

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Re:Reverse osmosis water leaching copper from brass?
« Reply #3 on: May 17, 2005, 06:12:22 AM »
rain water is never pure H20, because impurities in the air and exhaust emissions by natural processes ( volcanic eruptions, lightning oxidising nitrogen, the carbon cycle, etc.)
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Offline eugenedakin

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Re:Reverse osmosis water leaching copper from brass?
« Reply #4 on: May 17, 2005, 09:03:40 AM »
Hello David,

Xiankai is quite right about rain water.

This is only a suggestion, but you may want to add some regular tap water to your reverse osmosis water.  Usually, a 50/50 mixture will lower the formation of mineral stains on aquarium glass.

Just for my curiosity, what is your original purpose for using reverse osmosis water?

I looked at your recommended website.  Impressive pictures!!!  :)

Hopefully this helps,

Eugene Dakin Ph.d., P.Chem.
There are 10 kinds of people in this world: Those who understand binary, and those that do not.

UptheDownstair

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Re:Reverse osmosis water leaching copper from brass?
« Reply #5 on: May 17, 2005, 11:31:20 AM »
That makes sense about the rain water, I didnt think of that.

As far as using RO water, I did it becasue I live in Southern California and our tap water may as well be full of gravel it's so hard :-\  so my glass would be white with minerals in a matter of days.  I may try just mixing in a small amount of tap water or maybe an RO treatment which is supposed to replace lost essential minerals and trace elements viewable here  Thanks again for your help.  
-David


MyDogSpot

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Re:Reverse osmosis water leaching copper from brass?
« Reply #6 on: June 16, 2005, 10:23:53 PM »
For what it's worth, there are products that will raise the pH (make the water less acidic/aggressive) of RO water, maybe without adding yucky stuff that you don't want to feed your plants and frogs or see on your glass. Check with your local aquarium store or look online for "Kent pH Plus". I have no experience with this product, so do your homework! Nice pix on your web site, BTW.

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