Residue in Copper pipes: C-Flux

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Closefit

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While making plumbing changes in my house recently, I removed a section of supply copper pipe (cold) that was installed about a year ago and noticed that there is a green residue about 1" to 2" lengthwise, on each side of the fittings.

I was told that this is "patina". Most of it does wipe off with cold water and a paper towel, and leaves a dark, blue/green deposit on the towel.

When these pipes were installed a light coating of C-Flux was used on the fittings before soldering.

I have recenty heard about pinholes forming from flux left inside copper pipes. How likely is this to be a problem over time?

Should we expect a disaster now at some point because of the C-Flux?

Is it better to use water-soluble flux in the future or would No-Corrode or Oatey 95 prevent this problem?
 

FullySprinklered

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There's an epidemic of pinhole leaks in copper water pipes hereabouts. If you have the definitive cause of all this misery, I would sure like to know for sure what it is. I fix them, but I don't know what to tell the customer exactly what causes them.

I suspect it's a combination of bad pipe and bad water. I've posted before that some of the pipe removed from repair work acted funny when I bent it down to save for recycling. Take a piece of 1/2in copper pipe and bend it over your knee. It kinks and bends, and if you want to break it, you bend it back and forth several times until it breaks. The pipe with the pinholes, bent over the knee, rips open on the first bend. The second bent, it rips apart into two pieces. A little too easy, I'm thinking.

Time for some of our engineers to pipe up.
 

Jadnashua

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One thing that can cause grief with copper piping is the result of not using the proper reaming tool to reform the cut end (or omitting that step)- leaving a little lip there from the tubing cutter. Combine that with marginal or undersized piping that is supplying more water than design standards call for can cause turbulence, and literally erode the pipe over time. The most common location of the pinholes is within the foot or so of a fitting, especially if the pipe has hot water flowing through it. The copper tubing institute suggests NGT 5fps with hot water and 8fps with cold for a reason. See page 45 of their design handbook...

http://www.chem.mtu.edu/~fmorriso/cm3215/copper_tube_handbook.pdf
 

Reach4

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I had to look up "C-flux". Interesting.

I would think pinholes would to be due to acid (maybe pH<6.5) water, and compounded with using type M (red ink) copper.
 

Closefit

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While making plumbing changes in my house recently, I removed a section of supply copper pipe (cold) that was installed about a year ago and noticed that there is a green residue about 1" to 2" lengthwise, on each side of the fittings.

I was told that this is "patina". Most of it does wipe off with cold water and a paper towel, and leaves a dark, blue/green deposit on the towel.

When these pipes were installed a light coating of C-Flux was used on the fittings before soldering.

I have recenty heard about pinholes forming from flux left inside copper pipes. How likely is this to be a problem over time?

Should we expect a disaster now at some point because of the C-Flux?

Is it better to use water-soluble flux in the future or would No-Corrode or Oatey 95 prevent this problem?
 

Closefit

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I do NOT have pinholes now, I am just worried that the green stuff or flux residue from the C-Flux might cause problems over time.
Do I need to be concerned about what is already in place? Better to use water soluble flux in the future?
 

Jadnashua

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FWIW, if you don't solder often, the water based stuff is a pain. I think you're better off with what you have. According to the blurb I saw, it is not acidic based, and is rated for potable water, so you probably won't have any issues. I find that the stuff that has some tin or silver in it that tins the connection is easier to use. Pinholes, if they're caused by erosion or acid, tend to take awhile to occur. Defects in the pipe, could happen sooner. Give the pipe another couple of years, and you'd be somewhat grossed out about what's clinging to the insides of it.
 
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