RV Water Heater Anode Rod
An anode rod is used to help prevent corrosion of a steel water heater tank. The corrosive elements in the water attack the anode rod instead of the steel tank. The anode rod should be inspected yearly and replaced as needed.
Aluminum tanks have a special inner coating and do not use an anode rod.
Atwood tanks are lined with a material that acts as an anode rod, so therefore no anode is needed. Suburban uses a glass-lined steel tank and a sacrificial anode rod (magnesium) is used to prevent the steel from being attacked.
I don't see more Atwoods with corroded tanks as compared to Suburban tanks. (in my neck of the woods). I have seen anode rods in Atwood tanks (installed by previous owners) that were impossible to remove, and a welder friend explained that it is the different metals that causes this. The anode rod threads are steel and the tank threads are aluminum. This is why Atwood uses a nylon plug for the drain and does not recommend replacing it with a brass or steel one. I suppose if the anode rod was installed with teflon tape or a plumbers pipe sealant this problem would be eliminated, but would the customer remember to do this every time the anode is removed and replaced?
I hesitate to recommend anything to a customer that the manufacturer advises against. If something goes wrong the customer comes back, even years later, and says "You recommended such and such, now you owe me a new thingy"! Also, I figure that the manufacturer is the best one to recommend something to do with their product.
I do recommend flushing the hot water tank occasionally to get rid of the sediment and corrosive deposits in the bottom of the tank. Just pull the drain plug, allow it to drain, and direct a stream of water into the drain hole to agitate the sediment. Then allow it to drain, repeat until the water comes out clean. Do this about every other month (or more if your water has a lot of minerals) The flushing also helps to eliminate any hydrogen sulfide that may build up in the tank (causes the rotten egg smell in the water), and makes the heater more efficient.