You might be surprised to learn that there’s some serious drama going on inside your hot water heater tank. While you’re showering or doing the dishes, on the other end of the water line is a metal rod sacrificing itself in order to protect your water heater and keep it running for a few more years.

The Mighty Anode Rod

Your water heater’s anode rod is a simple thing -- a steel core wire coated with another metal, usually magnesium, but sometimes aluminum or zinc. It is inserted through an opening in the outside of your water heater so that water forms a connection between the anode rod and the inner walls of the tank.

But for such a simple device, it’s one of the most important components of your water heater because it keeps it from rusting. Read on to learn how it works.

An Electrochemical Process

To understand how a metal rod can save your water heater, let’s begin with a simple overview of how metal corrodes. Corrosion is a natural electrochemical process in which metals are oxidized, resulting in their deterioration. This happens when electrons flow away from the metals by way of an electrolyte, causing actual metal loss -- that’s why when rust gets out of control, it can eat a hole straight through the side of a hot water heater’s tank.

This process is always occurring, but the anode has a way to fight back. Anode rods are made from more active metals than the metals they’re designed to protect. So when the anode is connected to the at-risk metal by a volume of water, the electron loss of the anode is far greater than that of the less active steel water heater.

Of course, that means the anode rod will rust away over time until the active metal disappears completely, leaving your tank unprotected and susceptible to rust. That’s why it’s critically important to replace your anode rod before this happens. If you have your water heater inspected and maintained every year, it should be easy to catch a dwindling anode rod in time -- most anodes last for about five years, depending on the hardness of your water and how much hot water you use.

Choose Your Weapon

The three types of water heater anode rods have some important differences. Magnesium is the most common material used in modern water heaters, and it does an effective job of preventing rust. But it also has a weakness -- hard water. While magnesium rods will still work in areas with hard water, they’ll break down much faster, so it makes sense to consider an alternate material.

Aluminum anodes stand up much better to hard water, but they may also carry a certain risk. Aluminum exposure can cause health problems and may increase the risk of developing conditions including Alzheimer’s disease. As a precaution, it’s a good idea to avoid drinking hot water from the tap if you’re using an aluminum rod.

Zinc anode rods are actually made mostly of aluminum, but they contain a small amount of zinc to help counteract any sulfur odors that might be lurking in the tank.

If you need to inspect or replace the anode rod in your water heater, schedule an appointment with a trusted local plumber before it’s too late.