Replacing a Water Heater Anode Rod

What the Anode Rod Does

The anode rod is a sacrificial metal rod (typically magnesium, aluminum, or zinc alloy) suspended inside your water heater tank. Through a process called electrolysis, the anode rod corrodes preferentially instead of the steel tank lining. Once the anode rod is fully consumed, the tank itself begins to corrode, eventually leading to leaks and tank failure. Replacing the anode rod before it is completely depleted can double or triple the lifespan of your water heater.

Inspection and Timing

Check your anode rod every two to three years by turning off the water heater and unscrewing the rod from the top of the tank with a 1-1/16 inch socket wrench. If more than six inches of the core wire is exposed (the rod material has dissolved away), or if the rod is less than 1/2 inch in diameter, it should be replaced. In areas with hard water or softened water, anode rods may deplete faster — annual inspection is recommended in these conditions.

Removal and Replacement

Shut off the water heater (gas or electric) and close the cold water inlet. Drain two to three gallons from the tank through the drain valve to reduce weight and pressure. Use a breaker bar or impact wrench with a 1-1/16 inch socket to remove the anode rod — it may require significant force as it often corrodes into the fitting. If ceiling height is limited, purchase a flexible or segmented anode rod that bends during installation. Apply Teflon tape to the threads of the new rod and tighten it firmly into the port.

Choosing the Right Anode Rod

Magnesium rods provide the most protection but deplete faster in hard water. Aluminum rods last longer but provide less protection and are recommended for hard water or softened water systems. If your hot water has a sulfur (rotten egg) smell, switch from a magnesium rod to an aluminum-zinc alloy rod, which helps eliminate odor-causing bacteria. Powered anode rods use an electric current instead of a sacrificial metal and never need replacement — they are an excellent long-term investment for hard water areas.