water pipe grounding electrode
water pipe grounding electrode
(OP)
When you make a code compliant installation of a service in a building that is served by an interconnected metal underground water piping system, some of the current that should be flowing on the grounded conductor will flow on the parallel path provided by the water pipe. Is this a serious hazard? Should the code be changed to prohibit the use of the interconnected metal underground water piping system as a grounding electrode? Why or why not?
By "interconnected" I mean that the water pipe in building one is tied to a metallic main and the water pipes in the surrounding buildings are connected to the same main. This occurs everywhere where both the building water service pipes and the water mains are metallic.
Don(resqcapt19)
By "interconnected" I mean that the water pipe in building one is tied to a metallic main and the water pipes in the surrounding buildings are connected to the same main. This occurs everywhere where both the building water service pipes and the water mains are metallic.
Don(resqcapt19)






RE: water pipe grounding electrode
RE: water pipe grounding electrode
The issue of grounding water pipes is more complicated than this, I think. The NEC requires metallic water pipes be grounded even if they are physically isolated from the earth and cannot be used for a grounding electrode. To NOT ground the metal water pipe can present a hazard to someone if the water pipe should become energized for some reason.
The NEC does not allow ONLY a water pipe as a grounding electrode conductor - it must be supplemented by a made electrode of some kind. But this was not always a requirement.
I have seen situations where only the cold water pipe was used for a ground and hazardous voltages developed when the pipe was separated at a joint (because the neutral conductor was broken and the water pipe was the ONLY return path). That is a definite hazard.
Hope this helps.
RE: water pipe grounding electrode
The American Water Works Association reported in a July '98 article that on average one water worker per day receives an electrical shock beacuse of the grounded conductor current that is flowing in their water pipes.
Don(resqcapt19)
RE: water pipe grounding electrode
There has been a lot of discussion regarding grounding of water pipes of the years in the NEC panels (this is Code-Making Panel #5, I believe).
The requirement for grounding of water pipes is quite old, pre-dating nearly every other grounding requirement. If the electrical system is properly installed, there should be little or no current flowing in the water pipe. The main concern of the NEC recently has been the increasing use of non-metallic piping and the reduced effectiveness of the water pipe as a grounding electrode.
I suspect getting this requirement out of the NEC would be an uphill battle.
Your concern could be addressed by installation of insulating sections of plastic pipe to break up the continuity of the metal water pipe. This would not violate any codes that I am aware of.
dpc
RE: water pipe grounding electrode
The only way not to have current on the water pipe under the NEC would be to have the plumber install an insulating section in the water pipe outside of the building. If the metal underground water pipe enters the building, the NEC requires that it be used as a grounding electrode. As soon as you make this connection, some of the grounded conductor current will flow in the water pipe.
Don(resqcapt19)
RE: water pipe grounding electrode
There may be stray currents in the ground conductors, but unless the water pipe becomes the **only** low resistance path for neutral current, this does not create a safety hazard. If the water pipe becomes disconnected, even with current flowing in it, the current will just find another low impedance path.
I agree that there can be problems if the neutral conductor is broken for some reason. It takes a combination of more than one Code violation for this to become a major safety issue, at least for new installations. In most cases, the solution is to improve the overall grounding of the system.
RE: water pipe grounding electrode
Don(resqcapt19)