Water Heater Anode Rod
Installation and Replacement

Water heater anode rod, also known as the sacrificial anode, is the metal rod that protects the metal tank from corrosion helping it to last. Find out about different types; zinc, aluminum and magnesium and how it affects the heater' tank. Step-by-step guide on how to replace the anodes.

The water heater tank is usually constructed of steel and the inside surface, as it is exposed to the aggressive water action, has a glass lining bonded to the steel, to protect the metal tank. The anode rod is the secondary but also very important element in tank protection.

Types of the anode rods

There are several types of the anodes, some more some less used, made of different materials. Most of the heaters, especially economy class, have only one water heater anode rod installed. Such heaters usually come with the 6 year warranty. Other, more expensive units have thicker or more than one sacrificial rods, which allows the manufacturer to provide longer warranties.

The anodes can be found on the top of the water tank heater and are recognized by its hex-head plug end visible or hidden under the plastic cap.

Aluminum anode - recognized by the smooth surface on the plug.

Magnesium - has the weld bead on the plug. This type is the most used.

Zinc or Aluminum-Zinc is used where there is a high conductivity and due to the extremely hard water. These are providing an affordable solution for the rotten egg odor problem.

Powered anode - more expensive than standard type but effectively deals with the rotten egg smell. It is not sacrificial, but is permanent and provides a constant protection. It plugs into the wall socket.

Keeping the anode rod functional

Inspecting the rod once a year is what is recommended to keep the tank in the operating condition. The rod is submerged into the water and due to the aggressive water action is eaten away during the time. If you find the rod depleted by 1/2 of its volume it is time to replace it.


The most common complaint related to the water heater anode rod is the rotten egg smell.

If you have the water softener installed, which is used to reduce the mineral buildup within the tank, the soft water can significantly speed up the process of the anode depletion.

If you live in the area where the water supply has a high PH value (over eight) and there is an aluminum anode rod installed in the water heater, an excessive amount of aluminum hydroxide in a form of green, gray or blue "jelly beads" will form on the rod.

If the iron bacteria, which causes the rusty hot water, is present in the heater, it might cause the premature rod failure.

Keep in mind that the process of deterioration depends on the water conductivity. High conductivity makes the depletion to increase.

How to replace the anode rod

Keep in mind that the stored water inside the heater's tank might be hot.

  • Turn OFF water supply to the heater.

  • Turn OFF the gas and electrical supply. Turning the gas valve to OFF position is enough.

  • Use the garden hose and connect one end to the water heater drain valve and the other end to the open drain. Drain few gallons of water or below the outlet connection nipple.

  • Use the appropriate wrench to remove the anode rod (and the outlet nipple if the unit has one) from the heater. 1-1/16 inch, 6-point socket tool is used for the rod removal.

  • It is normal to see the signs of depletion on the rod, but if it is depleted over half of the original size, or you can see the steel core than you should be replacing the anode rod.

  • Once installed the new element follow the steps from the above in reverse order and to resume the operation use the instructions found on the label or manual.

As said before, periodic inspection and maintenance should be done at least once a year. The longevity of the water heater anode rod depends on several factors, and under normal conditions, you can expect it to last 3-5 years. If you prefer, you can buy a water heater, such as Rheem Marathon which does not use the anode, since they are made of plastic.

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