Archive for November 19th, 2012

Magnesium Water Heater Anode Rod: Seven Years Later

There never seems to be a good time to drain your water heater and check the anode rod, but I finally found a Round Tuit…

Pursuant to that comment, I drained a few gallons before applying the six-point 1-1/16 inch socket¬†and¬†loosening the anode rod without fuss or bother. I couldn’t get a good finger grip on the bolt head inside the enlarged hole, but a long-nose Vise-Grip pliers did the trick:

Gripping anode rod bolt

Gripping anode rod bolt

The first look showed a solid bar of corrosion:

Anode rod emerging

Anode rod emerging

You can see the 3/4 inch socket wrench in the background: I didn’t need the breaker bar this time!

The magnesium anode rod corroded down to the steel core wire just under the bolt head:

Anode rod - bolt

Anode rod – bolt

The entire rod was about half a foot shorter than the new one, but I cannot tell whether that much corroded away or rods have gotten longer (they’ve certainly gotten more expensive):

Anode rod - tip

Anode rod – tip

I sawed the rod to get it out of the heater, because I also wanted to see how much magnesium remained inside the corrosion. Quite a lot, as it turned out, so I suppose I could have reinstalled the rod and left it for another few years:

Anode rod - cut ends

Anode rod – cut ends

I don’t know where all the corrosion products went, because the water heater drained uneventfully, without clogging the valve or depositing a pile of crud at the end of the hose. There were a few particles, but nothing like the residue from the aluminum rod.

Then I cleaned off a new magnesium rod, tilted the water heater to get enough clearance, installed the rod with a wrap of PTFE tape, and reinstalled the water supply lines. I suspect the next owners of the place will be looking at it a decade down the calendar…

If I had more guts and less sense, I’d chuck the bar stubs in the lathe and turn off the corrosion to get some nice steel-core magnesium rods. The prospect of extinguishing a magnesium fire in the basement doesn’t entice me in the least.