Which Water Heater Anode Rod Do I Need?

By Shelley Frost

April 14, 2025

Is it time to replace the anode rod in your water heater? It could be if you have inconsistent hot water, a rotten egg smell, rusty water or loud popping noises from your water heater. The anode rod is designed to keep your water heater tank from rusting and corroding by sacrificing itself due to its reactive nature. That means you'll eventually need to replace the anode rod in a water heater.

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3 Types of Water Heater Anode Rods

Anode rods are designed to be more reactive than the metal that's in the tank itself. That way, the anode rod corrodes instead of allowing the tank to corrode. Tanks are usually made of steel, while anode rods are made of metals that will corrode more easily.

The types of anode rods are defined by the material they're made of, which includes:

Magnesium
Aluminum
Zinc

These traditional options are sacrificial anode rods because they degrade over time, but there's also a non-sacrificial type called a powered anode rod. This option is made from titanium and doesn't corrode over time. Instead, it prevents tank corrosion by using an electrical current. Powered rods also help with sulfur smells. You'll pay more for this option, but it doesn't need to be replaced frequently like other types.

What Are the Differences Between the Types?

Because each type of rod is made from a different material, it reacts differently to water and has unique benefits.

Magnesium Anode Rods

A magnesium anode rod corrodes easily and is suitable in areas with soft water where an aluminum rod won't perform as well. You can expect to replace a magnesium rod sooner because it corrodes faster, but that means it's doing its job well.

Aluminum Anode Rods

Aluminum anode rods offer a more durable option than magnesium. They usually take longer to corrode than magnesium anode rods, which often makes them better suited for harsh conditions like hard water.

Zinc Anode Rods

Zinc anode rods are actually mostly aluminum with just a small amount of zinc added. Because of that composition, zinc anode rods are also more durable than magnesium options.

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Which Type of Anode Rod Do I Need for My System?

Deciding between the types when you need to replace the anode rod in a water heater helps you get the best performance possible out of the part. A magnesium anode rod may work well in these situations:

You have soft water. A magnesium rod will likely break down too quickly if you have hard water.
Your water has a high pH level. Scale often forms with high pH levels, and a magnesium rod can help reduce it.
You want to save money. Magnesium rods are typically less expensive than aluminum-based rods.
You're concerned about the smell and flavor of your water. The magnesium often helps give water a fresher taste and gets rid of odors in the water.
You have a new water heater. This type is often recommended for newer models.

You might choose an aluminum anode rod in these cases:

You have hard water. The stronger material holds up longer in hard water conditions.
You have an older water heater. Aluminum is usually the preferred anode rod type for older water heaters.
You're changing your anode rods frequently. Because aluminum anode rods are more durable, you might need to switch to this type if your magnesium anode rods are breaking down too quickly.
You have well water. The higher levels of minerals, bacteria and dissolved solids in well water may cause a magnesium anode rod to break down too quickly. An aluminum rod provides more durable protection.

Zinc rods can be used in the same conditions as aluminum rods because they're made primarily of aluminum. People mainly choose zinc anode rods when water odor is an issue. The zinc can help counteract the rotten egg smell that often occurs when there are high levels of sulfur in the water.

The best way to determine which type of anode rod to use is to call a plumber. They consider the age of your water heater, the quality of the water in the area and any concerns to make a recommendation.

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