I was planning to inspect (and possibly replace) the sacrificial anode rod on my water heater. However, the union from the cold water supply to the rod looks differently from what I saw elsewhere. In particular, there is some kind of compound on the threads. What is it? Can I simply use a wrench to undo the union, or do I need to remove the compound somehow first? What should I use to remove it (either before undoing the union or afterward, before using PTFE tape to seal the union again)?

Union between a cold supply line and a sacrificial anode

2 Answers 2


The compound on the threads is most likely pipe thread sealant, aka pipe dope. The bigger issue is the copper pipe is soldered so there is no way for you to spin it without cutting it first. You would have to cut the pipe above the joint to allow you to loosen it. It would then be possible to loosen the fitting but would require a crescent/adjustable on the fitting and most likely a pipe wrench to hold the anode tight while loosening it.You would then have to either solder a new union on the pipe or use a push-connect fitting to reattach it. They make a flexible stainless hose with a threaded end to attach to anode and push-connect end to attach to the pipe which would potentially benefit later repairs. With that being said unless you are experienced with plumbing I would not attempt this without the help of someone who is.

  • As someone who wasn't familiar with plumbing, I dove into replacing my well water supply with city water supply. I did it (leak free for nearly 30 years, I might add) long before the internet was there to answer all my questions and without 10000 YouTube videos to watch all the wrong ways other people did it. This is a DIY forum - the goal is to help people who don't have experience learn from those who do.
    – FreeMan
    Commented May 24, 2021 at 11:55
  • Of course, getting help isn't a bad thing, but this should be something that someone with reasonable mechanical skills could tackle, and the rest of the info seems appropriate to me.
    – FreeMan
    Commented May 24, 2021 at 11:56
  • 1
    @FreeMan There are lots of things that are not difficult, but could go wrong when done by a novice. This answer was very helpful, as I now know what to look for if I want to do it myself, and that I should be ready to call for help if I mess up. In particular case, the "help" I referred meant that I might be able to complain to the company that did the installation since, per manufacturer's manual, the anode rod is meant to remain accessible for periodic maintenance.
    – Boris Bukh
    Commented May 24, 2021 at 14:59

What you are assuming is the anode rod appears to be your hot water outlet. The anode rod should be under that plastic cap you see in the pic toward the back of the water heater. Removing the plastic cap should expose the top of the anode rod which will require a 1 1/16" socket wrench to remove.
Before you do this be sure to close the water inlet into the water heater shut down the heating element and depressurize the tank. When reinstalling the anode you can use pipe thread dope or teflon tape on the threads.

  • No, it is indeed an anode rod. In my heater it is combined with the hot water outlet. See for example youtu.be/q3bY1UR77Dw?t=44 for a similar model.
    – Boris Bukh
    Commented May 24, 2021 at 11:50
  • Got it! Thanks! I never saw that before. I learned something.
    – HoneyDo
    Commented May 24, 2021 at 14:44

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