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ohmmm_gw

Does reverse osmosis water corrode copper plumbing? The answer ..

ohmmm_gw
12 years ago

The answer is YES.

I did a very unscientific study of this. I had installed a typical under the kitchen sink RO filter with a storage tank.

And one day I decided to test the water on a piece of copper.

So I took a small glass jar and put RO water in it. Then I took a brand new copper tubing hold down clamp and dropped it in the water. I covered the jar with plastic wrap to prevent evaporation and then waited.

Nothing much happened the first week or so. I changed out the water with fresh RO now and then. And after a month I began to notice the water had an orange tint to it. Hmmmm.

So I continued to change the water out once a week or so.

After about 3 months of sitting in RO water, the photo results are posted below.

Now, I realize, I did not use an actual piece of copper pipe. But I can make a pretty good guess, that if I did, the results would be similar.

You can see the particulate matter in the water. And you will also see that on the paper towel that I poured the water through. The corrosive effect was enough to reveal the base metal used on the copper clamp.

So anyone thinking about doing a whole house RO unit, better think twice if you have copper plumbing. Even if you have pex tubing or similar, the plumbing fixtures themselves usually have copper tubes on them.

{{!gwi}}

{{!gwi}}

{{!gwi}}

Comments (29)

  • justalurker
    12 years ago

    Sure it does... water is the universal solvent. When stripped of pretty much everything except the H and the O by an RO, water will try to dissolve and hold in suspension everything it can come in contact with.

    What you are describing is called leaching and is why PE tubing is recommended for POU RO units.

    Whole house RO units are not cost effective and require careful and thorough planning for complications such as leaching..

  • davidro1
    12 years ago

    water is the universal solvent.

    in the laundry forum I once posted that I used the universe's greatest solvent in my washing machine, at no extra cost. I often wash with cold water.

  • theplbginfo
    12 years ago

    Also whole house RO is extremely inefficient using between 3 and 5 gallons of water to produce 1 gallon of drinking water. If you're at all interested in water conservation RO is not the right choice.

    Sean
    theplumbinginfo.com

  • justalurker
    12 years ago

    That statement should be... If you're at all interested in water conservation whole house RO is not the right choice

  • asolo
    12 years ago

    RO is wasteful. Softeners are wasteful. Just about everything "civilized" society does is "wasteful". Then, again, every conservation-minded person I know lives in the biggest house they can afford. And, where I live, they all have RO units under their sinks.

  • AliceHasLeftTheBuilding
    12 years ago

    Interesting, Sean, that your handle references plumbing and then you display a lack of basic plumbing knowledge. There are two things that can be done with an RO to nearly eliminate "waste" water (a complete misnomer if you understand water balance at all, but that is another discussion entirely).

    1) Install a permeate pump, which will decrease "waste" flow per gallon of RO water produced.

    2) Plumb RO "waste" water to the household water heater rather than to drain.

    Quick, easy, inexpensive, and you can use your plumbing skills to accomplish the tasks.

  • asolo
    12 years ago

    Kinetico has at least two system designs that operate without back-pressure allowing much more efficient production. Assume others do, too, but don't know.

    How does one plumb RO waste-water so it goes to the water heater....that is non-pressurized gravity-drained source....into pressurized source?

  • rjh2o
    12 years ago

    Just a thought to share. We can waste food, paper, gas, time, electricity and many other things. Almost all pollutants can be removed from water. So if every drop of water on the earth has been here for time eternal. How can we possibly waste any water?
    RJ

  • asolo
    12 years ago

    Oh, wow.

  • AliceHasLeftTheBuilding
    12 years ago

    asolo - The effluent from an RO is not at zero pressure. It is lower than inlet pressure, however. A pump and a couple of check valves and you're good to go. There are systems already designed to operate this way.

  • asolo
    12 years ago

    News to me. Thanks.

    However, I can tell you the effluent from my RO systems -- now and for past 19 years -- has been and is, indeed, at zero pressure. The drain line goes directly into the zero-pressure drain-line under the sink.

    If you say this can be handled, I have no argument......except for the zero-pressure one.

  • justalurker
    12 years ago

    Asolo,

    "The effluent from an RO is not at zero pressure. It is lower than inlet pressure"

    Alice is correct and if you think about it you will realize that the effluent on the drain side of the membrane is being pushed through the drain line by a portion of the line pressure that makes it through the membrane.

    The simplest example of what Alice offered is... Watts Zero Waste RO

    http://www.costco.com/Browse/Product.aspx?Prodid=10034720

    And now there's a retrofit kit for existing RO installations.

    https://www.wattspremier.com/products.php?product=Zero-Waste-Retrofit-Kit

    You don't have to hook it up as the instructions illustrate. You can plumb it as Alice said if you know the correct way to do it.

  • asolo
    12 years ago

    The effluent from MY RO system -- past and present -- certainly IS at zero pressure. It exits down my sink's gravity drain. Where does yours go? If you're splitting hairs by saying there is enough "pressure" to get it to the entry-point of the sink's gravity-drain from the membrane cartridge, well, OK, ......but hardly the point I was making. I was comparing "practically zero" pressure effluent line against full-pressure hot-water line which I didn't understand.

    Now I do....thanks.

  • justalurker
    12 years ago

    Asolo,

    Let me see if I can explain this better.

    Most ROs installed in the last 5 years or so have a code required air gap faucet.

    Those faucets are higher (sink rim height) than the RO mounted under the sink.

    If the effluent from an RO is under ZERO pressure (as your ROs are?) then how does the effluent get to the height of the air gap faucet so it can cross the air gap and get down to the drain?

    Is it magic or is it pressure?

    Alice said "Plumb RO "waste" water to the household water heater rather than to drain". To the WATER HEATER. He didn't say anything about the hot water line. One could plumb the effluent to the cold side of the water heater using appropriate flow control and the effluent is no longer wasted..

  • davidro1
    12 years ago

    atmospheric pressure.
    This is "low".
    This is an air gap.
    Once water is ejected from any device, it is at that pressure.

    Some devices can handle ejecting water out, into atmospheric pressure.

    Whether or not a device will work well when it is expected to eject water out, into a pressurized line; This Is My Question.

    -

    I'm sure everyone can figure out that something additional can be rigged up, to take atmospheric pressure water and / pressurize it / pump it into a pressurized line.

    I believe the deeper stronger question is whether or not there is an RO system or an add-on which puts the potentially wasted water back into the pressurized system, and which does so adroitly professionally and warranteedly.

    " .... could plumb the effluent to the cold side of the water heater using appropriate flow control ..." Duh. I could have written that myself, and I have no idea what solutions there are!

    "...and the effluent is no longer wasted" Ditto.


    Hth

  • justalurker
    12 years ago

    Not atmospheric pressure... the pressure is that portion of the line pressure that pushed the water through the membrane.

    "I believe the deeper stronger question is whether or not there is an RO system or an add-on which puts the potentially wasted water back into the pressurized system, and which does so adroitly professionally and warranteedly"

    See my post above for links... Wed, Aug 3, 11 at 22:47

    ".... could plumb the effluent to the cold side of the water heater using appropriate flow control ..." Duh. I could have written that myself, and I have no idea what solutions there are"

    Then the solution exceeds you plumbing knowledge. And to repeat what Alice said... "A pump and a couple of check valves and you're good to go. There are systems already designed to operate this way".

  • bus_driver
    12 years ago

    Test the strap with a magnet to see if it is steel that is just copper plated. One of the photos looked like plating that had flaked away. I know little about RO, and cannot make an informed comment about it.

  • AliceHasLeftTheBuilding
    12 years ago

    Most, if not all, copper straps are copper-plated steel. Corrosion of a copper strap will look different from corrosion of a copper pipe.

    Copper is more susceptible to general etch corrosion (corrodes evenly over the entire surface). However, as plating on cheap parts tends to be uneven, corrosion is not visible until the thinnest spot is gone. At that point, copper in the water will deposit in discreet location on the carbon steel below, setting up galvanic corrosion - that is when you start seeing the rust in the water. Further corrosion of the carbon steel causes copper plating to flake from the surface.

    A copper pipe corroding in RO water would appear different. The corrosion would be much less obvious because it would be so even. It would take long enough that if you were using purely visual cues to determine corrosion, you might come to the erroneous conclusion that corrosion was not taking place.

  • oriddlero
    9 years ago
    last modified: 9 years ago

    Found good info and thought i would paste here. The i have a continues TDS on my RO input and output and my output is currently around 40 PPM. The Output feeds my Ice-maker and my Instant hot through copper pipes.... I was worried about corrosion and possible leaks and the below paste makes me feel better!


    Question:

    Will putting a whole-house reverse osmosis (RO) system on a house with copper pipe cause leaks?

    aquacareservice@embarqmail.com

    Answer:

    Will putting a whole-house reverse osmosis (RO) system on a house with copper pipe cause leaks?

    aquacareservice@embarqmail.com

    The simple answer to your question is yes. Copper plumbing that is exposed to RO water will cause pitting; however, the question begs for a more thorough explanation of whole-house RO. To begin with, when most people hear the term RO, they think of water that has had the mineral salts reduced by 99 percent. While this is good for life support water, this is not practical for domestic,whole-house, working water. It is good to keep in mind that the water for this type of application should have a finish TDS of 50-100 ppm.

    The product water off the membrane should pass through a small column of calcite or equivalent product, or it can be treated with soda ash to neutralize the acidic nature of the water to a less corrosive state. Bear in mind that these products must meet the NSF standard for food service.

    In addition to neutralizing the acid, calcite will add calcium carbonate to the water. If the water being treated by the RO still contains hardness, then an acid feed is generally needed to drop the pH to increase the solubility of the hardness. This will allow the membrane to reject high levels of hardness while preventing scaling. Therefore, passing the water through a softener to remove any remaining hardness is a very efficient way to provide the kind of working water that most homeowners would like in the first place.

    Gary Battenberg, Technical Director, Hague Quality Water International

    As a rule of thumb, if the TDS (total dissolved solids) concentration of the RO water is above 10 ppm (almost all is >10), it should not be aggressive enough to dissolve copper and cause leaks.



  • AliceHasLeftTheBuilding
    9 years ago

    This should NOT make you feel better about running RO water through copper TUBING.

    1. The above quotes (and if you cut and paste you really ought to provide a link or a citation) are addressing the use of whole house RO water through copper PIPES, which are either schedule 40 or schedule 80. Copper tubing, on the other hand is very, very thin and much more susceptible to pinhole leaks.
    2. You haven't provided your water's pH - the lower it is, the more corrosion you will have.
    3. The "rule of thumb" portion indicating that 10 ppm is not aggressive enough to dissolve copper is just plain incorrect as written. I suspect the gentleman was either hurried or his comment was edited. If he meant that it wouldn't be likely to cause leaks in pipes where water is pH-buffered, possibly correct, but tubing, as stated previously, is an entirely different matter. Further, if pH is below 7, copper pipe for RO water is a bad idea. RO water is nearly always below a pH of 7. 40 ppm RO water is aggressive enough to dissolve copper.
    4. Your RO water is your drinking water. The EPA action level for copper in drinking water is only 1.3 ppm - that's quite low. You could easily have that much copper in the you water after running through copper tubing, particularly if it has been sitting stagnant for an hour or more between uses.

    Using copper tubing to distribute RO water is just asking for trouble.

  • oriddlero
    9 years ago
    last modified: 9 years ago

    Here is a link to address your citation scolding: http://www.wcponline.com/expertview.cfm?ID=3717 

    I have not measured the PH of the RO output recently, but when i last measured it it was right around 7.

    I can fairly easily replace the copper with Poly all the way up the input for the refrigerator and input for the instant-hot fairly easily, however the instant-hot output has a ~12" copper tubing lead soldered to it (to handle very hot temperatures) so i guess i am beat there. Thoughts?

    #4 is an excellent point. I was actually thinking about that but i was not aware of the EPA action level and how to measure it. This alone is reason for concern. Thanks.

  • AliceHasLeftTheBuilding
    9 years ago
    last modified: 9 years ago

    There are very few drinking-water heaters that are rated for RO water. The ones that are rated for RO water use stainless steel tanks and tubing. The ones that aren't use carbon steel tanks and copper tubing.

  • oriddlero
    9 years ago

    Ugh. So one day my $400 instant-hot is going to explode in a steaming hot fireball of lava likely to destroy everything within a 10' radius?!

    Okay, maybe not, but you are making me think I should just pull the RO line off the instant-hot and feed it tap water from under the sink (ugh). Even if i were to hack the instant hot with a hot-water rated poly-line, the internal tank would still be susceptible to corrosion and the RO water may strip it and contaminate my drinking water. Maybe ill put a cheapo standard filter under the sink just for the instant hot.

    I'll replace the copper line to the refrigerator with RO rated poly to be safe. Thanks for the SOLID info! Its hard to find real data from educated people on this subject.

    BTW.. Congratulations, I am your first follower.

  • AliceHasLeftTheBuilding
    9 years ago

    Ignorance is bliss, right up to the point where it isn't, right?


    If it were my house, I would either plumb tap water to the existing instant-hot or replace it with one that is RO rated. Quick&Hot used to make one, but I haven't looked at them in about seven years so that may no longer be the case.


  • MrDoucheChill .
    6 years ago

    I had a whole-house RO system installed in my home in Fort Wayne, IN. I can speak from personal experience about some of the issues you may encounter.

    1) Efficiency -- The unit I used had a high pressure (160 psi) booster pump to run the water by the membranes. There was also a recirculate adjustment to send a percentage of the effluent back through the system, depending on the TDS of your source. At 350ppm source, I was able to get 4 gallons of RO water for each gallon of waste water (in about 1 minute.) That made the economics work out usably.

    2) Aggressiveness of pure RO water -- The water produced had less than 1 ppm TDS if desired. I found quickly that, if I let that pure water sit in my copper pipes for a day, the result was water that had >100ppm TDS -- initially, mostly scale from the pipes, and copper. That was a problem! I ended up bypassing original source water by the RO system to dilute the RO water to achieve around 120ppm TDS, which seemed to not leach copper anymore from the plumbing. This is critical, as too much copper in your body can cause a variety of health issues that would be otherwise difficult to diagnose (trust me on this.) (According to Wikipedia, the suggested safe level for copper in drinking water is 2ppm, not 100!) If your source has highly objectionable content, you'd want a different solution.

    3) When I used total RO water for washing my vehicle, there were no water spots! Unfortunately, this only lasted a short while until I figured out issue #2 above...



  • 75587ccf
    6 years ago

    Like you said, very unscientific test. You should have a control group. Put an identical piece of pipe in unfiltered tap water and compare results. Your HS science teacher will be very disappointed.

  • Fred S
    6 years ago

    It is unfortunate that you can no longer see the pictures. They were not really copper straps. They were metal straps coated with a thin layer of copper.

    Join two dissimilar metals, add a little water, and you have set up a circuit that can lead to some serious corrosion. Understanding terminology like electrolysis and galvanic reaction would tell you that the same thing would have happened no matter what type of water was used. It also explains why metal straps for copper pipe are coated in copper to begin with. In the absence of any random dust storm, the "sweat" on the outside of a copper pipe is just as pure as RO water.

  • William Lipp
    3 years ago

    If you dont want to worry about metal being damaged by RO water just add a remineralization filter after your RO