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

Posted by ohmmm (My Page) on
Wed, Aug 3, 11 at 12:24

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.

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Follow-Up Postings:

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RE: Does reverse osmosis water corrode copper plumbing? The answe

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..


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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.


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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.


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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.


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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?


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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


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RE: Does reverse osmosis water corrode copper plumbing? The answe

Oh, wow.


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RE: Does reverse osmosis water corrode copper plumbing? The answe

The law of conservation of water...

Water can neither be created nor destroyed... only billed for.


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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.


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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.


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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.


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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.


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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..


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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".


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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.


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RE: Does reverse osmosis water corrode copper plumbing? The answe

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.


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