Water Heater Anode Rod: Aluminum vs Magnesium

Tank-based water heaters are highly susceptible to corrosion, largely due to the pressure from the heat they produce and water acidity. Water heater anode rods are used to prevent rusting and extend the lifespan of your water heater, which means that the right water heater anode rod will play a major role in maintaining your water heater and keeping it functional for as long as possible.

When choosing an anode rod, you typically have the option of aluminum or magnesium. So how do you know which anode rod is best for your water tank?

Magnesium Water Heater Anode Rod

Magnesium anode rods are also known as sacrificial rods since they prevent rusting by diverting corrosion to themselves. This type of rod performs best with soft water since it is not as resistant to corrosion as aluminum anode rods.

Magnesium rods are more reactive and yield a higher voltage than the aluminum rods and therefore tend to have a shorter lifespan. This type of water heater anode rod is an ideal choice for in-line installations in cold water and screw-in applications.

For alkaline water, water with high levels of chlorine and chloramines, magnesium anode rods are the best option.


  • Magnesium anode rods are more effective in preventing corrosion since they produce a stronger current which helps to prevent corrosion in the water tank. They therefore perform better than aluminum anode rods. 
  • Dissolved magnesium has health benefits which makes it safer to use in your water heater.


  • Magnesium rods are more expensive than aluminum.
  • This type of rod does not last as long as aluminum.

Aluminum Water Heater Anode Rod

Aluminum anode rods, as the name suggests, are made using aluminum. This anode rod reacts slowly with water elements and therefore lasts longer than magnesium. These rods, just like the magnesium anode rods, divert corrosion from the water heater to themselves and in this way increases the durability of your water tank.

Aluminum anode rods typically act by producing a low voltage during electrolysis which slows down the rate of corrosion. You will find that most tank-based water heaters have aluminum anode rods.

These rods are the better option for areas with hard water and for water containing high levels of sulfates. Unlike magnesium rods, aluminum rods are more efficient at converting sulfates into hydrogen sulfides, which means that the water will not get the rotten egg smell that can result from the accumulation of excess sulfides.


  • Aluminum anode rods last longer than magnesium anode rods partly because they are less reactive. This means they will need to be changed less often.
  • Aluminum anode rods are more affordable than magnesium anode rods.
  • This type of anode rods will prevent water from getting the pungent smell of sulfides since they are more effective at converting sulfates into hydrogen sulfides.


  • Aluminum rods are not as effective at preventing corrosion as magnesium.
  • Aluminum rods produce byproducts which end up causing the buildup of sediment in the water tank.
  • Due to the sediment build-up caused by aluminum anode rods, there is a higher risk of clogs in the water filters and tap aerators.
  • Aluminum rods tend to get larger as they corrode. When this happens, especially after long periods of time, it becomes impossible to remove them.
  • When sediment settles at the bottom of the water tank, the water heater tends to get noisier.
  • Aluminum deposits are harmful to the liver, kidney, brain, and spleen.

Aluminum vs Magnesium: Which is Better?

The choice of which water heater anode is best for your needs will be determined by your budget and the level of hardness in your water.

If the water in your area is hard, then the aluminum anode rod is the best choice for you. In areas with soft water, the magnesium anode rod is the better option.

In terms of price, aluminum anode rods tend to be cheaper than magnesium rods and are therefore the best option if you are on a budget.

Since the aluminum anode rods are less reactive compared to magnesium anode rods, they generally last longer than the magnesium iron rods.

All things considered, the magnesium anode rods is overall the best choice since it is more effective at preventing corrosion and has health benefits when dissolved in water. Aluminum deposits are harmful to your body and can lead to health complications.

How Often Should You Check Your Water Heater Anode Rod?

  • It is important to check your water heater anode rod periodically. You can conveniently schedule it during your annual plumbing inspection.
  • Monitoring the status of your anode rod every 2 – 4 years will help you know the best time to replace it to avoid the complete disintegration of the anode rod.
  • Remember that the durability of your water tank depends on the proper function of the anode rod to prevent corrosion.
  • Replacing anode rods can be labor-intensive and expensive and sometimes it may be more cost-effective to replace the entire tank.

How Do You Know it is Time to Replace Your Water Heater Anode Rod?

  • If you find that the water heater pan is accumulating water, this means that your water heater anode rods are not working efficiently and they need to be replaced.
  • When your water heater starts to make loud noises when heating up, it can be due to the build-up of sediment in the water tank or high levels of corrosion in the water tank. In both cases, the water heater anode rods need to be replaced.
  • It is good practice to replace your water heater anode rod every 3- 5 years to keep your water tank corrosion-free.
  • If you find that you are getting clogs in the water filter and faucet aerators, this can be due to the accumulation of sediment and points to the fact that your node rod needs to be replaced.
  • If you notice a slimy substance when cleaning the faucet aerator, it may be time to replace your water heater anode rod.
  • You may notice a pungent or rotten egg smell coming from your water tank. This smell is caused by a lack of efficient conversion of sulfates to hydrogen sulfide. You may need to replace your rods to rectify the issue.
  • The more sediment there is in your water tank, the harder your heater has to work to heat the water. This results in higher bills. Old anodes will cause increased sediment build up in the water tank, so replacing them on time can save you money.
  • Overall, it is good practice to replace your water heater anode rod every 3-5 years to keep your water tank corrosion-free.


Ensuring that you have the right water heater anode rod will extend the durability of your water heater and prevent corrosion. While magnesium rods are safer and more effective in preventing corrosion, in areas with hard water, the aluminum water heater anode rods are more effective.