Question: are all anode rods the same thread size?
Answer: Thanks for the informative Web site! A: An anode rod is aluminum or magnesium cast around a steel core wire and hex head. For residential-type heaters, all anodes are the same diameter -- 3/4-inch. If you have a 30-gallon or what they call a low-boy -- a short, broad 40-gallon, you might have to shorten it.