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Do you know what this thin metal wire is? It's attached to the water line in my garage. It looks like it was cut off at the end. I can't see where the other end of the cable ends up - it runs behind the wall.

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    That's not so thin. That is a ground wire with good clamps. – SDsolar Sep 3 '17 at 1:46
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    Yep, ground wire. Likely the one for the main electrical service, given its location. Using two clamps is not the traditional standard (dunno what current code calls for), but it's very good practice. The pipe joints around that regulator do not make reliable electrical connections. – Hot Licks Sep 3 '17 at 13:11
  • In all candor, if that's thin by your standards, what is thick? Are you a welder? – Nick T Sep 3 '17 at 16:26
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It's your electrical service ground, comes from your panelbox.

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    It is a grounding conductor the pipe is the electrode that wire goes to the main panel. If they ever change your service to the home to plastic you will need to have driven rods, I have run into this several times in the recent past. – Ed Beal Sep 2 '17 at 22:38
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    Probably because the solder joints could develop resistance. Someone was making double sure the ground was uninterrupted no matter what happens there. – SDsolar Sep 3 '17 at 1:45
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    @NPM a jump like that is also very common in houses that have the water meter indoors. – Moshe Katz Sep 3 '17 at 4:16
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    It's also the bond for the water piping system -- which is important to keep something like an electric water heater or a dishwasher from giving you a nasty bite if it fails internally – ThreePhaseEel Sep 3 '17 at 5:08
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    While correct you could add some explanation and possibly links to further reading. – Notts90 Sep 3 '17 at 14:00
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First, that's hardly "thin" by house wiring standards. It looks like #8 or larger.

You've shown us one end of the wire. Check out the other end. It probably goes to your breaker box and is ultimately tied to the center tap of the transformer feeding AC power into your house.

If so, this is the grounding wire for your house's electrical system. It looks like it is connected to the copper water feed pipe into your house. That pipe goes underground and is a good earth connection. Since it was already present, it was used as the ground for your house instead of a separate stake driven into the ground for that purpose.

The two clamps are to provide a redundant connection to the copper pipe.

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    This isn't necessarily the grounding wire for the whole house electrical system. At least in the UK, grounding via water or gas pipes violates the installation code, because at some point out of sight the pipes may be plastic not metal. The specific purpose of what is in the OP's photograph is to make sure that the pipework on both sides of the joints are electrically connected, even if the joints themselves are corroded, unintentionally insulated with Teflon tape used to fix a leak, etc. – alephzero Sep 3 '17 at 18:09
  • @aleph: If that's all the wire was doing, then it would stop at the second clamp. Also, the fact that anyone cares at all that there is electrical continuity across the joints shows that the pipe is used for electrical grounding. – Olin Lathrop Sep 3 '17 at 18:27
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    #6 is the standard in the U.S. and many times this IS the only ground for older homes. I have found this in several areas where water mains were replaced and converted to plastic. – Ed Beal Sep 3 '17 at 23:33

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