larry moe 'n curly wrote:
I read that teflon tape should never be used on the threads of a water
heater anode rod because it electrically insulates the anode from the
tank and prevents it from protecting the tank. But I recently bought a
State brand heater containing two anode rods. One rod screws in the
normal way, but the other hangs from the hot water outlet by a 1" piece
of plastic, and it's definitely insulated from the tank. So does this
mean that the anode doesn't have to directly contact the tank?


Is there any possibility that that "second piece" is somehow in the
wrong place and it's really the "drop tube" for the cold water inlet?
You did call it a "rod" and not a tube, so excuse me if I'm making a WAG
in the wrong direction. But I too would like to know its function if
it's really insulated from the tank shell.

Maybe the plastic hanger is conductive? It wouldn't have to be really
low resistance to work, the current flow to an anode rod is only a few
hundred microamps. And, they do make conductive plastics, like the
static discharging laminates used on workbench tops to prevent
electrostatic charge damage of sensitive electronic stuff.

Re the teflon tape; I ran a short series of experiments years ago to
answer just that question. They showed that a reasonable wrapping of
teflon tape would not electrically insulate a pipe joint made up to
normal tightness. The teflon squeezed right out where there would be
metal to metal contact on the flanks of the threads and stayed where it
was needed to plug the "spiral leak path" between the truncated crest of
the male threads and the sharp bottoms female thread.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"