What's the best anode rod?
Regarding this, which is better aluminum or magnesium anode rod?
For harder water an aluminum anode rod is the best choice for your heater and if you live in an area with soft water then a magnesium anode rod is your best choice. Aluminum anodes tend to be cheaper than magnesium anode rods. A magnesium rod will generally last less than an aluminum rod.
Similarly one may ask, what size anode rod do I need?
If hidden an easy solution would be to remove the nipple on the hot water side with a pipe wrench and install a nipple outlet anode rod. Most gas or electric water heaters require a standard rod length of 44”. On some tall electric or solar storage tanks a rod 51” in length would be required.
In most cases, you will need to change your water heater anode rod approximately once every 6 years so long as it operates under normal working conditions. However, depending on the composition of your water, you may need to change the anode rod more frequently.