Theoritically everything in a properly grounded plumbing system should
be grounded at zero volts. BUT life aint perfect:(
Poorly conducting pipe joints, after all they are checked for leaks not
resistance, teflon tape, and a wide variety of possible fittings.
ground strap may not be jumping out meter, I had a washing machine
motor windings fail once producing a low voltage, improperly connected
main house ground, a poor ground or neutral connection in the main
panel, a doorbell transfoirmer wire intermittently connecting when the
hot water tank burner goes on, pipes can shake a bit, Dont laugh, I
found that once when I was a kid, doorbell rang at odd times. BIG CATCH
for me at 10 years old:) I am 49 today. Theres a million reasons that
can cause this:(
The BIG THING FIND AND FIX IT its might be a electrocution hazard! Say
standing in shower with your foot on drain you touch the faucet and
May be minor, but its not worth the risk!!