Water Heater Anode Rod Aluminum Vs Magnesium

Updated March 15th, 2020

Both have drawbacks… but there’s still a clear winner.

A water heater is a household essential, but it can also be a significant financial outlay.

So what can you do to make sure your tank-based water heater gives you the best value for money, and lasts as long as possible?

A crucial component to keeping your tank-based water heater in good condition is its anode rod. Anode rods help to prevent metal corrosion by releasing electrons into the water, in a process called electrolysis. Essentially, this means that in the highly corrosive environment of your water heater tank, where heat, acid and water are constantly putting the tank at risk of rust damage, the anode becomes a corrosion “sponge” by being the first component in the line of fire and soaking up all the damage. It does this because anodes are manufactured from highly reactive materials, like magnesium, aluminum and zinc.

There’s a catch to this arrangement, though.

The fact that your anode is highly reactive means that it can corrode surprisingly fast, and become a “fallen soldier” in the constant fight against rust in your tank. If your anode rod is too rusted to be functional, corrosion will start eating away at the metal in your tank. And even tanks that are lined with glass inevitably develop cracks over time… and start to corrode.

Below, we’ll outline how you can tell when it’s time to give your water heater anode rod an “honorable discharge” and replace it with a new one. But first, let’s compare the two most common types of anode rods you’ll find in water heaters today: aluminum and magnesium rods.

Water Heater Anode Rods: Aluminum Vs Magnesium – Our Review

So, you suspect your water heater’s current anode rod needs replacing, so you’re figuring out which type you ought to purchase as a replacement. Or, you’re buying a water heater, and you want to be informed about the components of tank-based water heaters – including anode rods – so that you can pick the most suitable model. We’re here to help you out with an in-depth review of the highly popular aluminum and magnesium anode rods, to help you make some decisions. We’ll analyze aspects like cost, durability and effectiveness, sum it all up for you in a hard-and-fast conclusion.

Keep in mind that “zinc” anode rods are really just aluminum with a tiny bit of zinc added. The presence of zinc can help to reduce the foul “rotting egg” sulfur smell that some water heaters produce.

Let’s be clear: both aluminum and magnesium anodes work well. But there are some differences that may significantly affect how they function in your household.


Aluminum is a highly abundant global resource. Magnesium is pretty easy to come by too… but it’s expensive to extract and refine. For this reason, aluminum rods are generally cheaper than magnesium rods.

Replacement Frequency

Aluminum is less reactive than magnesium, and therefore corrodes more slowly. You’ll have to go to the effort of replacing your anode rod less frequently if you install an aluminum rod. However… this may not actually be an advantage.


Because aluminum corrodes more slowly than magnesium, it may not be enough to combat corrosion in some water heaters. Your heater may slowly start to rust, despite having a functioning anode rod. A lot depends on the hardness of your water… see below.

Sediment Buildup

Aluminum anode rods have a distinct problem with releasing sediment during the corrosion process. This is a problem for several reasons.

  • A layer of sediment that has accumulated at the bottom of your water heater tank can cause your water heater to run loudly… some people report that it even wakes them up during the night.
  • Corrosive byproducts can wash into your plumbing system, and start causing problems there.
  • Floating byproducts also occasionally form. These are sticky, and can mess up the functioning of water filters and tap aerators.
  • Sediment from aluminum anode rods is a potential health hazard if consumed.

Magnesium anode rods, on the other hand, produce no harmful sediments. They definitely win this round.

Health Concerns

We’ve seen that zinc anode rods can cause a buildup of sediment in your water heater tank. The most unfortunate thing about this is the fact that aluminum can be horribly harmful to the body, potentially damaging the brain and other internal organs.

Magnesium, on the other hand, is actually healthy for you once it has made its way into your system. Among many other things, it can fight depression and lower blood pressure. So as far as health is concerned, installing magnesium anode rods in your water heater is a much better option.

Water Smell

The chemical reaction that takes place when magnesium erodes can sometimes produce hydrogen sulfide: enter the dreaded “rotting egg” smell. On the other hand, the zinc that’s often found in aluminum anodes is great at neutralizing the strong, unpleasant smells often created when metal gets together with water. Aluminum anode rods win this round.

Water pH

Hard water has a high pH: it’s alkaline. If you compare it to “soft” acid water, there’s a significant difference in the taste, and the way it interacts with various soaps and plumbing components. The pH of your water also changes the way your water heater anode rod functions. Soft water corrodes metal faster… and an aluminum anode rod may not be reactive enough to cover the bases here. If you have a low water pH, or soft water (this is easy to test for), an magnesium anode rod is your best bet.

Ease of Installation

When an aluminum rod erodes, it swells. Really old, used up aluminum anodes can be nearly impossible to remove, because the swelling has made them fit so tightly into their fixtures. Magnesium rods don’t have this problem. They’re generally quite straightforward to remove and replace.

Water Heater Anode Rods: Aluminum vs Magnesium – Our Conclusion

Magnesium anode rods are easy to install. They don’t produce nasty sediment problems, and they’re reactive enough to neutralize problems in acidic water. And they don’t pose any health risks, should you consume hot water from your taps… in fact, having one installed is ultimately good for your body. They may be a bit more expensive, and you will have to replace them more often. But we definitely think it’s worth it.

Here’s the one time you may want to exchange your magnesium anode rod for a zinc aluminum one: if your water spouts out alongside a pungent smell. If you do install an aluminum rod, don’t use the water for drinking purposes.

How to Tell if your Water Heater’s Anode Rod Needs Replacing?

Here are the signs that show you’re due for a new anode rod in your water heater.

  • If you inspect the rod, you can see 6 inches or more of the steel wire that forms the rod’s core.
  • There’s foam or sediment in the tank or filters.
  • The rod hasn’t changed in appearance since you installed it (this means it’s defective).

How to Replace an Old or Defective Water Heater Anode Rod?

If you love to DIY, and you’ve discovered that you water heater’s anode rod needs to be replaced, here’s a short, clear video tutorial that help you to successfully remove the old rod and install a new one.

11 Replies to “Water Heater Anode Rod Aluminum Vs Magnesium”

  1. Just recently changed my totally deteriorated anode rod and replaced it with an aluminum rod. This service had not been done by anyone for nearly 18 yrs so I suspect the heater may have begun to rust out from the inside. I read elsewhere that in my situation, it’s best to replace with an aluminum vs. magnesium rod as the magnesium rod would now further accelerate the rusting process. Have you found this to be true? I am concerned about aluminum toxicity but also don’t my heater tank to fail prematurely. Any suggestions advice? Thanks!

    1. I have the same problem with a 12 year old tank just thinking of replacing the rod for the first time, the article says magnesium provides better corrosion protection, so i would think magnesium would also be better to arrest further damage should the tank is beginning to rust

  2. From research that I have done they tell me that you’re better to have a magnesium anode rod then a aluminum one they say you shouldn’t drink the water after aluminum rod is installed is that true

  3. I have anew Bradford White gas water heater. It makes the faucets spit/sputter.
    We have relatively soft water. Metal pipes were replaced with pex hooked to existing copper. Bonding and grounding was tried to no avail.
    I think switching to an (aluminum anode) might cure the problem. We don’t cook with or drink from the hot water supply. But how about showers and dish washer use?

    1. The anode rod has no bearing on sputtering, neither does electrical grounding. It results from air in you plumbing. Couldnt say how the air is getting in your lines but it is not normal for sure. Usually happens to me when i have to shut the main supply valve off to do some maintenance like change a filter, but goes away as soon as you open a faucet.

  4. Update, switched to aluminum anode rod the sputtering and spitting has stopped. No more hydrogen sulfur gas problem .Thinking it over ,why would anyone drink from water heater water any way. (Ever see a cutaway of a used water heater inside.)
    I heard AO Smith ships theirs with aluminum rods from the factory. Different reviews have varying opinions which is best. Guess I will find out the long term effects myself. Shure would like a knowlegable person to chime in.

    1. Well, there might be a catch here: yes, you don’t smell hydrogen sulfide now and do not experience sputtering and spitting, but the very fact your system had it might mean that your water, as mild as it is, contains meaningful amount of sulfates or sulfides — some of which before magnesium might have broken into H2S and some magnesium oxide but now it is all staying in the water. I would think of testing the water for sulfides and sulfates if I used it for drinking/cooking.

    1. agree, having read around ten articles on this subject, this is the first one that really informs me on which kind of anode rod to choose for replacement

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