I have been thinking about doing a grounding and bonding document for Nick to look at for maybe using for continuing education for the Home Inspector. In this document would be this insert:
Much confusion revolves around metal water pipes and the NEC requirement for using these pipes for an electrode and bonding the metal pipes. The requirement to use the metal water pipe as an electrode and bonding of metal water pipes are two complete and separate requirements.
In order for the metal water pipe to qualify as an electrode it must have no less than 10 feet in contact with the soil and the connection to this pipe must be made within the first five feet where the pipe enters the building. Should there be less than ten feet in contact with soil then the pipe would not qualify as an electrode but there would be no harm in the pipe being bonded.
The requirement to bond a metal water pipe has changed over the years and many of the requirements have been completely deleted from the codes. One such requirement was found in 250-50 of past code cycles where the requirement was that any metal pipe must be made electrically continuous. This requirement to keep the water pipe electrically continuous was implemented for reasons such as the permission given in 250-80 to use a metal water pipe as an equipment grounding conductor for the replacement of three wire receptacles for two wire receptacles.
As the years past the electrical code making panels realized that the requirement to make and keep a metal water pipe electrically continuous could not be enforced therefore the permission to use a metal water pipe as an equipment grounding conductor was removed as well as the requirement to make a metal pipe electrically continuous.
In the past few code cycles the requirement to bond metal water pipes has lessened to the point that if a piping system is not entirely metal then the requirement to bond can be accomplished with the equipment grounding conductor for any equipment that is connected to the pipe.
In the classroom I use slides of past code cycles to show how the codes have changed over the years concerning the bonding requirements of metal water pipes. I also explain how some of the old requirements are hard to pass away such as the thought that there must be a bond across a water heater to bond the hot and cold water pipes together.
If one would take a moment to step outside the box and look at these metal pipes it would be easy to see that there is no requirement in either the electrical or plumbing codes to make and keep a metal water pipe electrically continuous. Should there be a need to do a repair to a copper water pipe a plumber could make this repair with a nonmetallic pipe and be compliant with the plumbing code. This repair would leave part of the metal pipe bonded and the rest not bonded. There is no requirement in either code that a bonding jumper be installed around this repair. If there is no requirement to bond around this type of plumbing repair then what would be the purpose of bonding around a water heater?