Bob F wrote:
"dpb" wrote in message ...
Bob F wrote:
"dpb" wrote in message ...
...
Not for corrosion protection, no--the wire is a grounding wire completing a
ground around the dielectric path.
Right - but does it defeat the protection offered by the dielectric union?
No, galvanic action is a direct contact. The ground wire, while there is a
potential yes, being dry is far less susceptible to the corrosion and it's
there where it can be seen, anyway. The dielectric between the two water
pipes themselves is still between the two dissimilar metals. It would be nice
if they were all the same material, but it's the lesser of the evils.

Just like a battery with a short across its terminals? I don't understand why
this is not a problem.

Cu/brass is ok...
Even when the other end of the valve is connected to galvanized outside pipe?
Well, no, that's a different connection--it's a direct connection between the
two dissimilar metals so strictly there should be one at each junction where
switching. As noted, brass being a mostly copper alloy is near enough in
potential to not be a problem.

But the brass is not similar to the galvanized pipe screwed into it.

I just go through saying that -- I was talking of the brass/copper
junction. If you have a brass/galvanized on the other end, it should
also be a dielectric connection.

There are compatible-metal grounding clamps available.

My experience has been however, that the grounding of a copper wire to
either galvanized (scrape through to the underlying iron) or black pipe
has not been a real problem in practice. It just doesn't seem to be an
issue that I've observed at that point.

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