I have seen numerous postings to the effect that you should not put
teflon tape on the threads of the sacrificial anode for a water heater,
as this will prevent the electrical conduction necessary for the anode
to do its job. SO, I put about 5 wraps of teflon tape on the threads
of my new anode, making sure all threads were completely covered and
then some. Placed the new anode in the water heater and screwed it in
till it started to offer some resistance, but not yet seriously
tightened. Measured resistance anode - to -heater, and lo and behold, 0
ohms. This should not be a surprise - once you put some torque on pipe
threads the only thing that can offer any resistance to such torque is
metal to metal contact between the threads.

wrote:
I have seen numerous postings to the effect that you should not put
teflon tape on the threads of the sacrificial anode for a water heater,
as this will prevent the electrical conduction necessary for the anode
to do its job. SO, I put about 5 wraps of teflon tape on the threads
of my new anode, making sure all threads were completely covered and
then some. Placed the new anode in the water heater and screwed it in
till it started to offer some resistance, but not yet seriously
tightened. Measured resistance anode - to -heater, and lo and behold, 0
ohms. This should not be a surprise - once you put some torque on pipe
threads the only thing that can offer any resistance to such torque is
metal to metal contact between the threads.

Hmmm,
That's no brainer. Tape fills in microscopic unevenness of metal
surface. It is not STRONG enough to prevent metal-metal contact.