[tblt]

I've seen houses with ground bonded to the copper water/gas pipes...and upon further inspection they were supplied with plastic piping outside of their property boundary. Yikes.

My understanding is that neutral goes to ground at the substation

[brewtide]

They are bonded to ground so that if a hot happens to run or chaff up against them, you don't have hot water or gas lines conducting in your house -- a dead short to ground will trigger a breaker overload (near) immediately assuming they are working correctly.

If these pipes were not grounded, they are just pretty scary conductive pieces of metal strewn throughout walls and ceilings, and usually terminating at a place where people physically contact, as well.

[mattpallissard]

> My understanding is that neutral goes to ground at the substation

Close. It's at the transformer.

North American "split phase" power has the neutral center tapped into the transformer winding. The two 120v lines are phased 180° from each other with respect to neutral. Line to line gets you 240v, line to neutral is half that, 120v.

Downstream in the breaker panel itself, the grounding conductor (ground) and grounded conductor (neutral) are bonded at the panel. The ground wire is basically just an alternate path back to the box.