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Thread: Strange corrosion in copper pipe in multiple locations in a ceiling

  1. #1
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default Strange corrosion in copper pipe in multiple locations in a ceiling

    Staying with a friend in a rental apartment in Loma Linda, CA for a few days. We noticed a slow drip of water coming from the ceiling, and called the maintenance department. They responded pretty quickly, while we were out touring museums and airports. Came back to find a 4' x 2' (or so) hole in the ceiling, exposing a length of 1" copper, where they had used worm clamps to hold small rubber patches over 2 small leaks in the pipe. They did a nice clean job, but as we inspected it closely, we found several more spots along the pipe that were leaking. All those spots were at places on the pipe with small spots of corrosion on them. Has anybody seen anything like this? There are corrosion spots along the pipe in about a 4' section, but no obvious source of the corroding agent -- subfloor above shows no signs of leaks, etc.

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  2. #2
    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    From the markings on the pipe it's type M copper with red lettering which is a light weight copper that's failing. Type L with blue lettering is what most codes require.

    John

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    That's true, but lightweight or not, I'm trying to figure out where the corroding agent came from. Looks like it must have come from above, after installation, but I can't find any evidence of any leakage on the subfloor above the pipe. It really doesn't matter, since it's not my house, and it's up to somebody else to fix it, but my engineer gland is acting up .

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    Moderator & Master Plumber hj's Avatar
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    It is not "corroding" from an external source. The tubing is failing, and the blue is caused by the water seeping out. It is probably a hot water pipe.
    Licensed residential and commercial plumber

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default

    Wow, thanks... I never thought of that. Assuming they'll replace that section of pipe, I'll try to get a piece and see what the cross-section looks like at a blue portion. We're pretty sure it's not hot water, though, and based on the limited layout we can see, we can't figure out what it's for.

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    Moderator & Master Plumber hj's Avatar
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    Default copper

    You will probably see a "row of barnacles" inside the tubing on the bottom.
    Licensed residential and commercial plumber

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Looking forward to finding out. The pipes serve the fire sprinklers, which complicates the repair process somewhat, but it should be done in the next few days.The maintenance supervisor has promised us the cut-out section of pipe to play with. He's seen this before, and thinks that if they used too much flux when assembling things, it might have lain around in the pipe before the system was charged with water, and started a corroding process. We doubt that for several reasons, but we'll see.

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default The smoking gun

    The official sprinkler guy showed up and said yeah, it was flux inside the pipe that started a corrosion process. He had apparently seen a lot of flux, in pipes from 4" down to 1/2", or whatever size served the sprinkler heads. It sounded like strategic sabotage to me, to ensure an ongoing source of business as the pipes slowly decayed. They'd already replaced all the heads, and were starting again. Anyway, he whacked out a 4' piece with the worst exterior, and gave me 18" of it for a souvenir. Here's pictures of the inside, showing HJ's barnacles:

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    and outside, showing the streaks from the pinhole leaks dribbling down the pipe:

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