Copper Water Line Gages, And Usage ?


Hello,
Live in a 35 year old house outside of Boston.
Had a leak in a Copper water pipe that the plumber finally found.
Unfortunately, I forgot to ask him if it was in a hot or cold line, as this might, perhaps, be meaningful ?
Anyway, what surprised me was that it was pinhole leak in the middle of a run. Not at a joint or fitting, etc. Right in the middle of a line.
Apparently they used the thinnest Copper they could find when they built the place. I used a caliper on it, and found it to be 0.028, which I guess is a grade M (outside diameter of 5/8 inch)
But, it still should take the household pressure without any problem, I would think. True ?
The plumber replaced it with heavier wall stuff of approx. 0.038, which is probably Type L
Questions:
a. What might make a pinhole leake in the middle of a clear run ? I guess the pinhole can be considered as a corrosion type of breakthrough.
b. How common is something like this is the thinwall Type M tubing ? What causes ?
c. 35 years ago, was this (Type M) a common Copper gage they used for household hot and cold water lines ?
d. Is it still allowed, or the Code prohibits it now all over ?
Any thoughts on this would be most appreciated.
Thanks, Bob.
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might have been bad from day one, a weakness in the origiinal copper that ook 35 years to fail.
I wouldnt worry about it...
any chance a fastner like screw rubbed it?
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Robert11 wrote:

finally tore out the copper and replaced it w cpvc. should have done that from the beginning and saved a lot of aggravation. once they started they kept on springing leaks all over that dam copper. we was on a well.
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One leak is not bad, but I had the same thing hapen to a 35 year old house I had. After about 3 leaks and then spending a lot of time under the house trying to get the leaks stopped (fix one, another place would start) I had it replaced with the Pex (or whatever) plastic pipe.
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The OP shouldnt panic, a single leak in 35 years is nothing to get upset about, perhaps a previous owner hung a picture there and happened to damage the line.
now if more leaks occur then its ime for PEX.
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Robert11 wrote: ...

Probably was pit from manufacturing process that took that long to finally break through. While not common, it's not unheard of for a new section to have a leak initially.
Corrosion pitting is a combination of material and water chemistry. One possibility is as someone else noted a touching piece of other metal such as a truss bracket, etc. that can rub or be an electrolysis potential.
M was (and is) pretty common simply for cost -- it takes less Cu to make thinner wall (obviously) so many contractors used it--particularly houses built "on spec" rather than on contract where there wasn't a specific buyer to satisfy or look over the materials.
I know of nothing in the Code that would proscribe it...nor should there be, really. Even in your case it's been 35 years which ain't too bad annoying as it is...
--
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This happened in my parents' house. Pinhole, middle of a run, no damage or anything. At least decades old. Luckily all the plumbing in the house is exposed so it was easy to spot (middle of the kitchen ceiling) and fix. (Why don't we do it like that now? :)
So this is a normal failure mode. Why that spot? ... a tiny inclusion of foreign material when the pipe was made; a scratch from the plumber's watch fob; cosmic ray. Unknowable.
I'm pretty sure M and L are both ok by most codes for residential use in the U.S. and Canada. One pinhole in 35 years is considered tolerable. It's up to you to ask for the better stuff if your budget allows.
Chip C Toronto
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