The metal lining of your water heater can and does rust, and this shortens the life of the heater and turns your hot water brown. To prevent this, there's an anode rod in the heater, which is designed to rust instead of the lining. Replacing this rod regularly keeps rust out of your hot water.
The Sacrificial Rod
The anode rod is also called a sacrificial rod because its function is to deteriorate in place of the water heater liner. It is made of aluminum, magnesium or zinc -- all are metals that will corrode before the steel lining does. Corrosion of the anode rod protects the steel lining because it reduces the electrical charge in the water.
Replacing an Anode Rod
When the anode rod wears out, it can no longer do its job, and the steel lining may start to rust. Once that happens, the water may turn rusty, and the tank itself may need replacing. Anode rods typically last four to five years. To replace one, unscrew and pull it out from the top of the water heater tank, then drop in a new one and tighten it with a wrench. Be sure to turn off the water and the heater's fuel or electricity before you do this.
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