A tank-type hot water heater can last for 10 to 15 years with the proper care. An important part of that maintenance is the anode rod.
Water Heater Parts
An experienced plumber can replace all of a hot water heater's components except for the tank. A homeowner must purchase a new heater when the tank rusts out and fails.
Steel forms the outside shell of the tank. The inside has a glass lining, which can develop microscopic cracks over time and lead to rusting of the shell.
All tank-type storage hot water heaters come with an anode that is suspended inside the steel tank. The anode has a steel core with either a magnesium or aluminum coating.
The purpose of the anode is to prevent the corrosion of the outside steel shell. An electrochemical reaction corrodes the anode rod before the steel tank, thereby protecting it from rusting, which results in a longer life.
Corrosion will use up the anode rod over time, and it will have to be replaced. The anode rod should be examined every 3 to 5 years by an experienced plumber and replaced if needed.