Op here, couple thoughts...
Magnesium rod versus aluminum rod question.....
Here is what back of package says:
The sacrificial magnesium anode equalizes aggressive water action providing cathodic protection for the tank. The anode rod is a very important factor in tank life and should only be removed for inspection or draining. Replacement of the anode rod is recommended when consumption or weight loss is greater than 75%. With regular inspection and replacement of anode rod, tank life can be greatly extended. Frequency of anode replacement will vary depending on the water conditions and usage. Operating the water heater without the anode voids the manufactures limited warranty and shortens the tank life of the water heater.
In most conditions, anode rod should last at least one year. If your magnesium anode rod does last for one year, you may want to use aluminum anode rod (p/n 232768). Alum rods react slower and should be used only in situations where magnesium anode rods do not last one year.Other thoughts.
Being the manufacture recommends replacement when 75% of rod is gone. That 75% went somewhere, I wondered what the daily recommended amount is for magnesium. Turns out its good for you. The benefits of RVing...who knew?
http://www.webmd.com/vitamins-and-supplements/lifestyle-guide-11/supplement-guide-magnesium
