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Anode rod passivation

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Don_175
Don_175 Member Posts: 126
in Domestic Hot Water
Hello,

I recently replaced the anode rod on our Geospring heat pump water heater. It is about 10 years old. We bought the house several years ago, and I doubt the previous owner did any maintenance.

I had bought a segmented aluminum replacement rod as the ceiling is low, and we are on well water. The hardness is around 150 when we had the water tested.

The rod looked amazingly intact with a heavy calcium coating. In fact, I had a little bit of a hard time getting the rod out. Is there any way to prevent the passivation? Or do I just replace the rod more regularly?

There was very little crud that came out when I flushed the water heater.

Thanks
Don

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  • Larry Weingarten
    Larry Weingarten Member Posts: 3,291
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    Hi @Don_175 , Just to be clear, it was the segmented aluminum anode you had installed a few years ago that had the scale build-up and you're calling passivated? As aluminum gets used up, it does produce a LOT of blue-grey goo and can be harder to pull up and out of the tank. With your water, I'd be looking at replacing that with a segmented magnesium anode. Aluminum produces less current than magnesium in a given water and is best used in softened or pretty conductive waters. Also, a powered anode might be worth looking into as it should need no further work (aside from checking that it's still working) once it has been installed.

    Yours, Larry
  • Don_175
    Don_175 Member Posts: 126
    edited November 2022
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    Larry Weingarten said:

    Hi @Don_175 , Just to be clear, it was the segmented aluminum anode you had installed a few years ago that had the scale build-up and you're calling passivated? As aluminum gets used up, it does produce a LOT of blue-grey goo and can be harder to pull up and out of the tank. With your water, I'd be looking at replacing that with a segmented magnesium anode. Aluminum produces less current than magnesium in a given water and is best used in softened or pretty conductive waters. Also, a powered anode might be worth looking into as it should need no further work (aside from checking that it's still working) once it has been installed.

    No. The rod I pulled out was a standard solid rod. I'm assuming magnesium as I couldn't bend it to take it out. I had to cut it with a hacksaw. I had read that aluminum was better for well water or hard water and especially well water with sulfur in it.
  • mattmia2
    mattmia2 Member Posts: 9,637
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    If it were me I would go with the powered anode.

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