Water Heater Anode Rod Aluminum Vs Magnesium

Updated August 31st, 2022

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

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

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

Its anode rod is crucial to keeping your tank-based water heater in good condition. 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 and sum it up for you in a hard-and-fast conclusion.

Keep in mind that “zinc” anode rods are 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 some differences 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 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 releasing sediment during the corrosion process. This is a problem for several reasons.

  • A layer of sediment 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 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 that aluminum can harm the body, potentially damaging the brain and other internal organs.

Magnesium, however, is 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 when magnesium erodes can sometimes produce hydrogen sulfide: enter the dreaded “rotting egg” smell. On the other hand, the zinc 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 how it interacts with various soaps and plumbing components. The pH of your water also changes how 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. A magnesium anode rod is your best bet if you have a low water pH or soft water (this is easy to test for).

Ease of Installation

When an aluminum rod erodes, it swells. 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 are 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 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 install an aluminum rod, don’t use the water for drinking.

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 your water heater’s anode rod needs to be replaced, here’s a short, clear video tutorial that helps you to remove the old rod and install a new one successfully.


13 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.

      1. Actually, the Bradford White owner’s manual and my conversation just now with a Bradford White rep says that the number one cause of faucet sputtering when the hot water has been turned on is the anode rod.

        The anode rod Bradford White puts in their water softeners is made of magnesium. When the magnesium rod is doing its job, a byproduct of the reaction its having with your water to prevent the inside of the tank from rusting is hydrogen, the production of hydrogen gas. Normally, there’s not enough hydrogen produced to cause sputtering. However, for people with softened water or alkaline water, it can be a problem because softened water or alkaline water reacts more heavily with the magnesium, thus producing more hydrogen gas, so much more that it causes sputtering. What’s sputtering out isn’t air but pure hydrogen, so take care not to expose any spark or flame near the faucet when it’s sputtering.

        Bradford White recommends contacting them if sputtering from your faucets when the hot water is turned on is a problem after installing a new Bradford White water heater and they will send you a replacement andode rod for it made of aluminum-zinc, which reacts more slowly and so is better for a soft-water or alkaline environment that accelerates reaction and which does not produce any “out-gassing,” i.e., which is that sputtering.

        Also, you know the problem isn’t air in your plumbing because the sputtering wouldn’t persist but would stop as soon as whatever finite amount of air that got into the plumbing while changing the water heater bled out. If you’re having sputtering that’s ongoing, that’s been going on for days, weeks, months perpetually, that’s not air in your plumbing. Plumbing is a closed system, water- and air-tight, so the only way air gets into a line is when you’ve opened it up to work on it. Once you close it all up again, any air that got in may cause sputtering in the faucets for a short time, but then the sputtering stops because more air can’t get in. Even if there were some crack or broken seal in your plumbing lines, air wouldn’t get in but instead water would come out of it since the water in your plumbing lines is under pressure, so instead of air in your plumbing you’d have a water leakage problem.

        A second possible cause of sputtering from the faucet that never happens when you’ve only got the cold water on but only happens whenever you have the hot on is steam. If your water heater is turned up too high, since hot water flows out of the top of a water heater and because heat rises, molecules of water that have been heated to above boiling but because of pressure inside the plumbing haven’t turned to steam suddenly expand into steam as soon as that pressure releases as it leaves the faucet, thus sputtering. It’s not all the water that’s boiling hot, so the water flowing out isn’t boiling hot or even scalding but just individual molecules. It’s sort of like how you can superheat molecules of water in a microwave such that the water isn’t boiling but as soon as you move grab it or clunk it down on the counter, those molecules suddenly burst into steam and the water boils up as steam releases, the only difference being that with the microwave, you’re giving superheated water molecules within the water (water molecules heated to above boiling temperature) a vibration they need to convert into steam rather than a release of pressure they needs to convert into steam, so in this case, it’s also not air that’s sputtering out of your faucets when the hot water is on, nor is it hydrogen gas, but is steam, instead.

  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.

    2. I am researching an AO Smith commercial gas HWT that is having issues and it comes with a magnesium anode. Just an FYI

    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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