Water Heater Anode Rod: What It Does, Problems & Replacement

The anode rod protects your water heater tank from rust and corrosion. When it wears out, it can cause rotten egg odors and shorten the life of the tank.

If your hot water smells like rotten eggs or your water heater is aging, the anode rod is likely involved. This guide explains how it works, how to diagnose problems, and when to replace it.

Quick Answer

The anti-corrosion anode rod attracts corrosion inside the tank. When it’s depleted, the tank can rust and odors may develop. Replace it every 3–5 years or when significantly worn.

What the Anode Rod Does

The anode rod is a sacrificial metal rod installed inside the tank to protect it from corrosion.

• It’s made of magnesium, aluminum, or zinc
• It attracts corrosive elements in the water
• It prevents the tank lining from rusting

Without a functioning anode rod, the tank will eventually corrode and leak.

Symptoms of a Bad Anode Rod

As the anode rod is consumed protecting the tank from corrosion, it can begin causing sulfur odors or other problems—especially in homes with mineral-heavy or softened water. These are typical symptoms and their causes:

• Rotten egg smell: Bacteria reacting with the rod
• Rusty or discolored water: Tank beginning to corrode
• Shortened water heater life: Loss of corrosion protection

See Water Heater Smells Like Rotten Eggs for more detail.

How to Check the Anode Rod

Inspecting the rod helps determine whether it needs replacement. The anode rod is usually mounted vertically into the top of the water heater and often has a large hex-shaped head about 1 to 1 1/8 inches across. On some water heaters, it is exposed on top of the tank; on others, it is hidden beneath a plastic cap or integrated into the hot-water outlet fitting. Because the rod extends several feet down into the tank, you’ll need enough overhead clearance to pull it out. In tight spaces, flexible segmented replacement rods are available.

1. Turn off power or gas
2. Shut off water supply
3. Locate the anode rod at the top of the tank
4. Fit a deep socket over the hex head and turn counterclockwise. Because anode rods are frequently seized in place, you may need a breaker bar for additional leverage. Having another person steady the tank can help prevent twisting plumbing connections.
5. Inspect the rod for heavy corrosion, deep pitting, exposed steel core wire, or sections that have been eaten away. A healthy anode rod is usually about 3/4 inch thick and fairly uniform in shape. If large portions are reduced to less than about 1/2 inch thick, covered with thick calcium buildup, or the inner steel wire is visible, the rod should be replaced.

How to Replace an Anode Rod

Replacing the anode rod can extend the life of your water heater significantly.

1. Turn off power or gas
2. Shut off water supply
3. Relieve pressure by opening a hot water tap
4. Remove the old rod as discussed above
5. Install the new rod (use Teflon® tape on threads)
6. Tighten securely and restore water supply

Because water heaters are often located in basements or closets with low ceilings, flexible anode rods are available for installations with limited clearance.

Repair vs Replace

Repair or Replace?

Replacing an anode rod is one of the least expensive ways to extend the life of a water heater. Because the rod is designed to corrode instead of the steel tank, installing a new one can significantly slow internal rusting and help prevent premature tank failure.

If the water heater is otherwise in good condition and not leaking, replacing a depleted anode rod is usually worthwhile—especially on a unit less than about 8 to 10 years old.

However, replacing the anode rod will not fix a tank that is already failing internally.

If you notice:

• Rust-colored water
• Water leaking from the bottom of the tank
• Heavy corrosion around fittings
• Noticeable loss of hot water temperature
• Moisture or rust streaks on the tank itself

…the tank may already be badly corroded and nearing the end of its life.

Important: A leaking or internally corroded tank cannot be permanently repaired. If corrosion has eaten through the tank, replacement of the entire water heater is usually the only practical solution.

See Repair or Replace a Water Heater.

When to Call a Pro

Some situations require professional help.

• Rod is stuck and cannot be removed
• Corrosion is severe
• You are unsure about the process or don’t have the necessary tools

FAQs

How often should an anode rod be replaced?
Typically every 3–5 years, depending on water quality.

What causes the rotten egg smell?
A reaction between bacteria and the anode rod producing hydrogen sulfide gas.

Can I remove the anode rod permanently?
No. Removing it will accelerate tank corrosion.

Are there different types of anode rods?
Yes—magnesium, aluminum, and zinc each have different properties.

Next See

• Water Heater Smells Like Rotten Eggs
• Noisy Water Heater
• How to Flush a Water Heater
• Repair or Replace a Water Heater

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