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Water Heater Anode Rod - Modern water heater tanks are constructed of steel with a thin glass lining to protect the steel from corrosion. The glass lining will eventually crack, but there is another level of protection from corrosion inside of the tank: the water heater anode rod.
What is a Water Heater Anode Rod?
A water heater anode rod is a long metal (usually magnesium or aluminum) rod that attracts the corrosive elements from water in order to protect the steel tank. Anodes are often screwed into the top of the tank and go almost all the way to the bottom. It is sometimes called the sacrificial water heater anode rod because of the way it sacrifices itself in the tank to protect the steel.
Because the molecules of magnesium and aluminum give up their electrons quicker than steel, rust will only occur on the anode rod while it still has metal to sacrifice. By diverting the rust to only occur on the anode rod, it can extend the life of your water heater. The water heater anode rod’s lifespan depends on a few different factors, namely: quality of the water, the water temperature, amount of use the tank gets, and the overall quality and construction of the tank. If there is salt added to the water as in the case of softened water, anodes corrode at a faster pace.
Anode Rod Options
Adding an additional anode rod should be considered if your model allows for it. By taking up more surface for it to absorb corrosion you can increase the life of your water heater even longer. However, it may not be a good idea if you are having odor problems as it can make the problem worse.
If you are thinking about adding an additional anode rode to your tank, make certain that both are made of the same metal. If one is magnesium and the other aluminum, the magnesium will be consumed more rapidly and you won’t get the desired outcome.
Another option is a powered anode rod or impressed-current anode. These do not sacrifice themselves in order to protect the tank, they instead are plugged into an outlet and stops the tank corrosion by releasing a continuous but small amount of electric current in the water, which prevents the electrochemical reaction that usually causes metallic corrosion. The benefits of a powered water heater anode rod are that they last much longer than a regular anode rod, they usually can take care of smelly water, and are better for the tank if you have soft water in your home.
Anode Rod Types for Different Tanks
There are two anode rod configurations, hex-head, and combo or outlet anodes. Hex-head water heater anode is often found on its own port on the top of the tank. Depending on the model, the hex-head might be exposed or under a plastic cap halfway from the center to the edge. Combo rods have a steel nipple that is plastic lined and used in the hot water port. Frequently tanks with a longer-term warranty have one combo and one hex head, although some just have one combo rod with no option for a second rod.
Anode Rod | Conclusion
Most tank water heaters last approximately 10-12 years, and they are not cheap to replace. Anode rods last 3-5 years and are about 20-50 dollars. Powered anode rods are about 250 dollars. By periodically checking your anode rod and replacing it when necessary, you can prolong the life of your water heater significantly.
For more resources on troubleshooting gas heating systems see our gas heating systems troubleshooting guide.
Water Heater Anode Rod
