NFPA 13 prohibits the use of the underground pipe that supplies a fire sprinkler system as a grounding electrode.
How on earth did the Corelating Committee let that one get by. That is direct conflict between National Fire Protection Association Standards 13 and 70. I could understand it occurring between 2 or more standard writing organizations but to have it happen within the organization that writes both standards is mind boggling.
At the dawn of the electrical age there was a fear among water utility operators that the use of any underground water piping as an electrical ground would cause galvanic corrosion between the dissimilar metals then commonly used in water distribution piping. A joint meeting of senior members of both the NFPA and the American Water Works Association (AWWA) ended with agreement that there was insufficient evidence that such corrosion was, in fact, happening to warrant concern about the possibility. The 2 organizations made an arrangement to periodically check for the occurrences of such corrosion. I do not know how long that mutual monitoring continued but I have never seen any allegation that such corrosion is happening. For all I know that monitoring arrangement continues in some form today. Now because 2 different NFPA Correlating Committees didn't work together we have a direct conflict between 2 NFPA standards. This raises some interesting questions.
If there is only one water lateral from the utility's water main and the sprinkler piping diverges from that common supply in the served premise is the common water service lateral an "Underground Metal Water Pipe" or is it "Sprinkler Piping?"
I haven't seen the Victaulic pipe couplings used underground on metal pipe but not being a pipe fitter I could easily have missed a common practice. Are there other types of pipe coupling that accidently introduce insulating joints into the water supply lateral underground? If the lateral is free of insulating joints does that make it an "Underground Metal Water Pipe?"
Tom Horne