Water heater sacrificial anode rods are metal rods generally screwed into the top of the tank that attracts corrosive elements in the water. They are “sacrificed” for the healthy survival of your steel-lined water heating tank.

As a general rule, magnesium anode rods work better than aluminum/zinc anode rods but don’t last as long. In any case, water heater anode rods are essential for protecting your tank from corrosion, but they eventually wear out after around 3-5 years, depending on many factors including the hardness or softness of your water.

Without a working anode rod, your water heater tank will be vulnerable to rust, corrosion, and other damaging effects of chemicals and minerals in your water supply.

Here’s a diagram showing the inside of your storage water heater and where sacrificial anode rods come into play:

How Does a Sacrificial Anode Rod in a Water Heater Work?

In order for the anode rod to work correctly in a water heater, the anode rod must possess a lower, more negative, electrochemical potential than that of the water heater’s steel composition to be protected. All metals have a negative voltage, but the lower the voltage (more negative), the more active the metal is considered to be.

The negatively charged electrons create a higher voltage to flow from the anode rod to the steel tank causing the anode rod to corrode instead of the steel water heater tank, or other exposed metals such as electric elements. Another way to think of anode rods is that they are “weaker” metals, which take the brunt of the corrosive elements before the stronger metals that make up your water heater tank.