my house played a joke on me.
Picked up a 50's style lighted medicine cabinet at an antique store and
finally replaced the cheap piece of junk that was there.
After it was all put in I realized I had forgotten to check the cabinet
to make sure it was properly grounded.
I put the leads of my meter between the cabinet and the sink's faucet
and damn...no ground! Pissed me off as I had everything mounted all
ready and did not really want to rip it apart.
Then realized the faucet is being fed by plastic pipe and is not
grounded. Going directly to the cold water pipe...all OK.