ETS-Lindgren HI-3624(A) Survey Meter - Manual (Page 15)

Practical Application and Use | 15
A phenomenon which has recently received some attention in regard to
residential magnetic fields is the flow of earth currents via plumbing lines or
telephone cables buried beneath the home. In some cases, it has been noted
that 60-Hz magnetic fields exist within a home, even when the home is not using
any electrical power (the circuit breakers have all been turned off at the main
electrical service box of the home). This observation has, in some cases, been
related to the flow of currents beneath the home on pipes or cables. It is not
unusual for currents, related to other neighbors' use of electricity, to flow back to
the electrical supply via low resistance paths formed by metal plumbing pipes or
wires used for telephones as opposed to the electrical system neutral wire. In
such cases, it is possible to measure magnetic flux densities within the home
without any apparent reason if the power to the home has been shut off.