I'm both frustrated and confused. No one had mentioned to me, even the owners manual that says about replacing the anode rod, and zero instructions come with the new anode rod, said there needs to be metal to metal contact on the threads.

I hate leaks so I used both some dope and pink teflon tape. No leak for sure! But now I think i have to take the new rod out and clean all the threads so it makes contact. Why do threads need to contact? Isn't the rod itself enough to attract the corrosive elements in the water? Could I run a wire from the anode head to touch any other part of the heater on the outside to not have to remove the anode?

Update 2020-05-17: Measured resistance, 26 ohms on a spot with some less than clean metal. ~0.1 Ohm on a clean shiny metal edge of the tank fitting (was scuffed up by the impact socket for sure) and I cleaned the bolt head with brake cleaner and also scuffed with a wire brush (dremel drill).

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    Do you have an ohmmeter/multimeter? May 15, 2020 at 2:07
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    The rod does not work by attracting and removing corrosive elements in the water. The rod is one electrode of an electrochemical cell with the steel tank being the other electrode. The two electrodes must be connected so that electrons can flow from the rod to the tank enabling the rod to sacrificially protect the tank from corrosion. May 16, 2020 at 18:06
  • Your finding of 0.1 Ohm is only possible with metal to metal contact. The resistance of the parallel path through the ions in the water is greater by orders of magnitude. All threaded pipe for either water or natural gas is sealed at the joints with dope or tape but the joints must be electrically conducting. May 17, 2020 at 17:53

2 Answers 2


The anode rod must be electrically in contact with the steel of the inner tank. Only this will confer sacrificial protection of the steel tank. The statement in the instructions is correct. See sacrificial metal. Google "sacrificial protection".

Even though you used dope and teflon tape you may well have electrical contact through the threads because the threads cut through the dope and tape. To check you would check the electrical resistance between the end of the anode rod and the fitting the rod threads into. You should get close to zero resistance (zero ohms).

If the measured resistance is not close to zero, you could perhaps just tighten the rod more and achieve metal-to-metal contact. I am sure you don't want to overtighten because you might be thinking of replacing this rod later, but you must achieve metal to metal contact for rod to do its job.

Also, overtightening could damage the tank. It could be that the threads of the anode rod must be only lightly coated with pipe dope for metal-to-metal contact to occur. You will just have to determine what you have.

EDIT Glad to hear you got 0.1 ohm. I just went out and measured the resistance across the threaded brass joint on one of my outside faucets (warm climate tract house with faucet supply coming out of the soil) and got 0.1 ohm. I installed this with dope and tape because it leaked the first time with just tape.

I measured the resistance across the "dielectric union" supply line to my water heater and got hundreds of ohms.

  • Thanks Jim, seems like there is confusion on this for sure as I have 2 different answers now. Rheem tech support said that no metal contact was required. ? To clarify, my owners manual did NOT say to ensure metal-metal contact. It also doesn't say to use teflon either, it's super vague. May 17, 2020 at 14:31
  • My guess is that Rheem meant no additional connection is necessary. When the anode rods are installed at the factory they do put pipe dope on the threads. I think the faces of the threads squeeze out any dope and make metal to metal contact. The dope stays in place in the space between the ridges and grooves. May 17, 2020 at 17:24

The anode rod does not have to have metal to metal contacts at the threads. The material itself is full-filling the purpose of rusting first. So if it is not leaking, you are good to go!!!!

  • For a metal to act as sacrificial - two dissimilar metal where one is more active in water, will form a weak current between the two metal, with the active metal (aluminum/magnesia) giving up electrons before the less active metal (steel). The two metal do not physically have to be connected. The majority of instructions on replacing the anode rod states to use PTFE tape and/or piping compound . None I have found states any requirement that the threads must make physical contact. IF it was a necessity, every instructions from OEM would make this a critical point for replacing the anode rod May 16, 2020 at 20:06
  • Actually the two metals are connected, by the water the metal is in. May 16, 2020 at 20:07
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    Thanks @Programmer66, I called the Rheem tech support they also said that no metal contact was required. Though this topic clearly has a lot of cofusion, seeing how there are 2 different answers here now. May 17, 2020 at 14:27
  • It is called an anode rod, not simply a protective rod. An anode is one electrode of an electrochemical cell which also must have a cathode. Current cannot flow through the cell unless there is a conducting path outside the cell to complete the circuit. May 17, 2020 at 17:33
  • Thanks all for the downvote, while the OEMs and not one of the plumber sites states that a metal to metal contact is required. May 18, 2020 at 18:39

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