I took a borescope today and looked at the inside of my Atwood heater:
At this point, I am not sure if it is corrosion or scale. When it gets warmer outside, I am going to attempt to flush it with a mixture of vinegar and water. If some of it comes off, I am assuming it is scale; but if there is no change, then I am going to assume it is corrosion.
I also measured between the brass overflow valve on the water heater to the aluminum threads that the nylon plug screws into, and I measured 0 ohms.
This means there is contact in water with dissimilar metals, so my conclusion then is that corrosion will occur inside the tank. Why Atwood does not see the need for an anode is puzzling... perhaps its part of planned obsolesce.
But, I have no data showing failure rates in Atwood heaters due to corrosion, so perhaps the corrosion rate is low enough that Atwood does not think an anode is required.
At any rate, corrosion has to be happening due to the dissimilar metal contact, whatever the corrosion rate is. So whether you use an anode or not probably just depends if you want dissolved magnesium or dissolved aluminum in your hot water.
Camco makes two different anode/plugs for Atwood heaters.
For me, it is a good indicator to keep taking a jug of distilled water along for coffee and meal preparation.
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