Field Production by Water Line Currents
A large part of Silencing the Fields (almost a third) is devoted to the residential fields that are created at a house or in a neighborhood by the flow of electric current into the water supply system, where such current is present.
Some grounding-system current will flow into the plumbing at any house that has its electrical system grounded to an all-metal city water supply system (which is a very safe and effective type of grounding). This includes most houses built in this country before about 1960. Part of the return current flowing back from a house to the power company will go into the water system, rather than back by way of the electrical supply (service) wires. That missing current leaves a current deficit (a "net current") in the service cable to the house -- as well as creating a net current in the water pipe grounding paths, which carry the missing current through the house and out into the city water system. (Then at any neighbor's house having the same type of grounding, part of the current flows back to the power company wires, creating elevated fields there as well.)
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And both of those currents make specially high fields near their paths because they are "net currents."
Why do net currents cause more fields? In general, if supply and return currents are equal in an electrical cord or cable (so there is no net current), the fields they create will cancel each other. Thus an important object for us is to try to be sure the return current flows by the same path as the supply current -- as is the case normally with most currents in a house. For instance, if one amp of current flows to a lamp in its lamp cord, then one amp of current returns by the other wire in the cord, since there is no other way back to the wall outlet.
Thus to remedy the fields from water line currents at a house, we can simply block the metallic path to the iron water main that provides an alternative path for part of the return current from the house. We can insert a short length of plastic water pipe, for instance, and thereby force the entire neutral current to return to the power company by way of the service cable that brings electric power to the house. There will be no net current, because supply and return will be equal.
However, that current blockage alters the grounding, and may have safety implications even though all electrical code requirements are met.
Fortunately there are often other ways to reduce such fields in a house, without actually disconnecting our grounding from the water main - ways that alter where the net currents flow, or how big they are. For instance, as shown in this illustration from Chapter 29, net-current fields from the electric supply cable can be "relocated" by changing the cable's path. Part III (58 pages) of Silencing the Fields covers a variety of such methods for reducing or relocating the fields produced by these water-line currents, with their usefulness depending on the situation.
