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Grounding to a cold-water pipe is pretty common in the US, and is allowed under certain narrow circumstances by the national code (subject, of course, to being

Grounding to a cold-water pipe is pretty common in the US, and is allowed under certain narrow circumstances by the national code (subject, of course, to being disallowed by local codes.). Specifically: NFPA 70 250.52(A) Electrodes Permitted for Grounding. (1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductor(s) or jumper(s), if installed.

coryrc 4y ago
Even more so, it's usually mandatory to ground your panel to incoming water line when it is metallic. But that's for the electrical panel, not a single random outlet.
- marcus0x62 4y ago
  Sure, but that’s about providing a ground path for the water line in case it becomes accidentally energized, not necessarily providing a ground electrode for the electrical service. In other words, you’d have to do that even if the metal water piping was not eligible to be used as a ground conductor: NFPA 70 250.104(A)(1) General. Metal water piping system(s) installed in or attached to a building or structure shall be bonded to any of the following: (1) Service equipment enclosure (2) Grounded conductor at the service (3) Grounding electrode conductor, if of sufficient size (4) One or more grounding electrodes used, if the grounding electrode conductor or bonding jumper to the grounding electrode is of sufficient size The bonding jumper(s) shall be installed in accordance with 250.64(A), 250.64(B), and 250.64(E). The points of attachment of the bonding jumper(s) shall be accessible. The bonding jumper(s) shall be sized in accordance with Table 250.102(C)(1) except that it shall not be required to be larger than 3/0 copper or 250 kcmil aluminum or copper-clad aluminum and except as permitted in 250.104(A)(2) and 250.104(A) (3).

coryrc 4y ago

Even more so, it's usually mandatory to ground your panel to incoming water line when it is metallic. But that's for the electrical panel, not a single random outlet.

marcus0x62 4y ago
Sure, but that’s about providing a ground path for the water line in case it becomes accidentally energized, not necessarily providing a ground electrode for the electrical service. In other words, you’d have to do that even if the metal water piping was not eligible to be used as a ground conductor: NFPA 70 250.104(A)(1) General. Metal water piping system(s) installed in or attached to a building or structure shall be bonded to any of the following: (1) Service equipment enclosure (2) Grounded conductor at the service (3) Grounding electrode conductor, if of sufficient size (4) One or more grounding electrodes used, if the grounding electrode conductor or bonding jumper to the grounding electrode is of sufficient size The bonding jumper(s) shall be installed in accordance with 250.64(A), 250.64(B), and 250.64(E). The points of attachment of the bonding jumper(s) shall be accessible. The bonding jumper(s) shall be sized in accordance with Table 250.102(C)(1) except that it shall not be required to be larger than 3/0 copper or 250 kcmil aluminum or copper-clad aluminum and except as permitted in 250.104(A)(2) and 250.104(A) (3).