The most common source of elevated magnetic
field readings in homes is electrical current on a water pipe. This is more
accurately described as neutral current diversion into a metallic
plumbing and grounding system, also referred to as plumbing current,
or ground current. Small commercial buildings can also exhibit this
condition. The situation exists when some of the current that would
normally return through the electrical service line feeding the building
is instead channeled into the grounding system, where it
returns to the transformer by way of alternate paths, including water pipes, the public
water main, and neighboring residences. This unbalanced current creates
a strong magnetic field with a wide spatial extent. The type of power distribution
system used in the U.S., in combination with important National Electrical
Code grounding requirements, establish the underlying conditions for this
problem to occur. It is more common in communities with moderate to high
housing density, especially those served by overhead power distribution
lines, but it can occur anywhere.
Drawing by Ed Leeper from Silencing the Fields (more info)
This undesired current flow can be
blocked very effectively, and in a manner that is code compliant, by the
installation of a dielectric coupler, or insulating coupling, in the water supply line to the building. Several
strong cautions are necessary before this work is planned. In some extreme cases, the problem
results from a partial failure of the power feed to the building (open neutral), and can
represent a potentially serious electrical shock and fire hazard. If intervention
is undertaken without an analysis of the nature of the problem, and if
the integrity of existing electrical facilities is not verified, extremely
hazardous conditions can be created. In addition, a large sum of money
will have been spent on an ineffective solution. We routinely resolve plumbing
current problems, and can coordinate the activities of local service providers
at any location through telephone consultation. There is a flat-rate fee of $125 for this service.
One type of dielectric coupler (union) installed in water line.
Misinformation abounds on the causes and correction of plumbing current problems.
Some sources advise driving additional ground rods (does nothing). Others even
tell you to disconnect required grounds from the water pipe in the building (dangerous!). Still
others say it cannot be fixed, and suggest suing the local electric or water utility (waste of money).
This is not a mysterious issue. It is understandable, explainable, quantifiable,
and in almost all cases, fully correctable. For those who wish a further explanation,
the following should be helpful:
- Type I plumbing current is described above.
It results from current utilization within the building where the analysis
takes place. The magnitude of the problem tracks the changing power load as electrical
devices switch on and off. When power to the building is turned off, it goes away.
Correctable as described above.
- Type II plumbing current is also described above. It
results from current utilization in another building besides the one under analysis.
Power to the building under analysis can be turned off, and the utility meter can even be removed, but
the current still flows and the magnetic field is still present. The current magnitude can be seen
to vary as electrical devices in another building switch on and off. This problem can occur because
of a defective neutral in the service drop to the other building, but this is not always the case.
Type I and Type II often exist together in the same building, and can add or subtract. Correctable
as described above.
- Type III plumbing current exists when primary neutral
return current (often from the utility transformer feeding the premises) flows over the
secondary portion of the neutral system into the building and crosses over into the plumbing
system, usually because of a deficient neutral conductor in the utility distribution system. This is
less common and of lower magnitude than Types I and II. Correctable as described above.
Related Issue:
Earth Current refers to the flow of primary
return current through the earth back to the serving substation. It is not the type of
current discussed on this page, but it is accurately referred to as ground current.
Primary neutral return current enters the earth at
any point where the electrical system neutral is connected to a grounding electrode. This
condition is a consequence of the multi-grounded-neutral (MGN) system that is
universally used for power distribution in the US. This system evolved
early in the history of electrical power use because it offered a number of
safety advantages. A fundamental precept of the system is that the earth (which is conductive)
functions as a current return pathway to supplement the neutral system, and to handle
transitory overvoltages due to lightning or high voltage faults. This is a major route by which primary
current returns to the substation. The utility goes to great length to build
and maintain a low resistance ground grid at the substation to handle the current.
There may be adverse consequences from earth current flow,
such as the establishment of earth surface voltage gradients. This is especially true
for the dairy farming industry, where it is one component of the stray voltage issue.
It also becomes significant in the design of residential environments for electrically
sensitive individuals.
