My sister called me the other day and said that my mom and dad were
feeling a slight tingle when they touched both the kitchen faucet and
the metal sink. (They live about 300 miles from me)
I mentioned that the only wires that should be under the sink would be
for the garbage disposal, so maybe it was related to that. She said it
happens even with the disposal off.
Since this tingling was something new, I offered this possibilty:
There was water leaking onto some electrical part of the disposal
the disposal switch has been wired incorrectly for years,
switching the neutral instead of the hot. Therefore, there is always
power available at the disposal looking for a return path and the
water is now providing that path through the disposal housing to the
sink/faucet/copper plumbing and then into the user.
My sister called an electrically-talented friend who looked under the
sink, saw water dripping from the disposal and then checked the
wires. Sure enough, the neutral was being switched.
He rewired the switch and I'm driving over to replace the leaky
disposal this weekend.