Re: Water Pipe Bonding
I first thought this was an easy question. The water pipe is a grounding electrode, and the GEC is to be sized per 250.66. Case closed. I would not question having a GEC to a water pipe being larger than a GEC to a ground rod. I would have asked the question from the other direction. My question would have been more along the lines of "why is it OK to have a smaller GEC, when you are connecting to a ground rod?"
Then I took a closer look at 250 (a dangerous task, as we all know). I am now confused by something entirely different. 250.104(A)(1) says, in part, "The metal water piping system shall be bonded to (some things) OR to . . . grounding electrodes." Wait a minute. I though the water pipes were a grounding electrode. :confused:
So we must be talking about water systems that do not connect directly to the incoming water supply. Drain lines and "grey water" lines, perhaps? So I have to ask, not having done this type of thing before: Do you bond all water lines? In every room? On every floor? If you see a pipe, should you see a wire also? Or if you bond once, on the first floor, do you not have to bond anywhere else? What is the actual practice? :confused: :confused:
Charles E. Beck, P.E., Seattle
Comments based on 2014 NEC unless otherwise noted.