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Old 06-30-2012, 09:32 AM   #16
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Badly corroded AC copper line


Sticking out of the floor there in the middle, to the left of the big line, what looks like a copper line with a white cap...what is that?


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Old 06-30-2012, 09:39 AM   #17
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Badly corroded AC copper line


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This may be slightly off topic, but you got me curious. I am in Southern US as well, Southeast, Miami, Florida and I see soft copper pipes being used for water supplies installed underground all the time. It runs from one manifold to another manifold under the slab with no sleeves and much of them are still working after 40, 50 years. Now those are type L copper and are in direct contact with the ground (mostly sand), and the only thing they do is to have a section of sleeve where the lines pass through the slab.

Is the HVAC copper different from water supply copper to cause a problem when in direct contact with ground?
No, not different, and you won't see much degradation in sand (at least in my experience). We see this mostly with "clay-ey" soil, which is very prevalvent here in the South Carolina/Georgia area. I too have seen many copper lines buried in the ground that seem to have done fine, but I've seen too many of them that were heavily corroded in a very short time.
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Old 06-30-2012, 09:49 AM   #18
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Badly corroded AC copper line


So the copper line is run inside galvanized electrical conduit?

If so, then remember that copper and galvinized metal don't really mix very well. Combine the two and you often get a "galvanic" reaction, which just means that one (or both) of the metals will corrode. You can stop this - for example, plumbers use dielectric unions when joining copper to galvanized pipes - but in your case I don't see how you'd stop the two from contacting at some point. You could coat the copper, but that would rub off fairly quickly. A better solution would be to use PVC conduit, which won't react with anything.
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Old 06-30-2012, 11:24 AM   #19
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Badly corroded AC copper line


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Originally Posted by scottmcd9999 View Post
No, not different, and you won't see much degradation in sand (at least in my experience). We see this mostly with "clay-ey" soil, which is very prevalvent here in the South Carolina/Georgia area. I too have seen many copper lines buried in the ground that seem to have done fine, but I've seen too many of them that were heavily corroded in a very short time.
OK thanks. I know both houses I lived in had underground copper pipes. But where I live it's basically sand.

The code varies though. Down here in Miami, they even allow you to have soldered fittings underground. Although personally I don't do it, I always either use soft copper to remove the need of a fitting. I don't trust a fitting below the slab.
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Old 06-30-2012, 11:27 AM   #20
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Badly corroded AC copper line


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Originally Posted by scottmcd9999 View Post
So the copper line is run inside galvanized electrical conduit?

If so, then remember that copper and galvinized metal don't really mix very well. Combine the two and you often get a "galvanic" reaction, which just means that one (or both) of the metals will corrode. You can stop this - for example, plumbers use dielectric unions when joining copper to galvanized pipes - but in your case I don't see how you'd stop the two from contacting at some point. You could coat the copper, but that would rub off fairly quickly. A better solution would be to use PVC conduit, which won't react with anything.
Yes. that's weird they used electrical conduits to sleeve a copper. So from your description is may have accelerated the corrosion. They may have added the sleeve to protect the copper from being banged and dinged by weed eaters or whatever. They should have sleeved it with PVC, or simply bury it deeper.

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