Water Heater Anode Rods: What it is & How to Replace it


anode rods

It is a very important component of a water heating system. Not only does it keep the storage tank running smoothly but it also significantly lengthens the lifespan of the unit itself!

Part of your water heaters maintenance includes replacement of the anode rod about every 3 years. Many people do not even know what an anode rod is not to mention that they need to replace it.

Right now, you may be wondering to yourself, ‘what is a water heater anode rod?’ An anode rod is a sacrificial steel core wire that is wrapped with aluminum, magnesium, or zinc. Anode rods work by attracting corrosive particles found inside your water heater tank to protect the tank liner and reduce the risk of explosion. Anode rods should be replaced every 3 to 5 years depending on your water quality.

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If the anode rod in your water heater looks like this, it’s time to replace it to protect your water heater’s longevity.

Are Water Heater Anode Rod Sizes Universal?

Anode rods are not universal. Anode rods vary in length and material. Some anode rods are installed at the top of the water heater tank while others are attached to the water heater hot water outlet.

The diameter of residential water heater anode rods is universal at 3/4 inches. However, the length and type of the anode rod may not be the same. Also, some anode rods are attached to the top of the water heater while others are attached to the hot water outlet.

Some anode rods are 33 inches in length while others are 44 inches in length. You may need to cut it down to fit your water heater if you have a smaller unit (often referred to as a ‘low boy’ or ‘stubby’) that is only 30 or 40 gallons.

Now that you know anode rods are still universal in diameter but vary in length and type, let’s take a closer look at this in more detail below. We’ll discuss the different types and sizes of anode rods and explain how to cut one down to properly fit your specific water heating unit. We’ll also discuss how often they should be changed, whether (or not) all heating units require anode rods and which one to purchase in the future, should the need arise.

So, if you’re ready to learn more about anode rods, then let’s get started!

What are the Different Types of Anode Rods?

There are 5 types of anode rods. However, the majority of all water heaters will have an aluminum, magnesium, or zinc anode rod. Let’s look at each below:

Magnesium Anode Rods

This is the most common type of anode rod used in residential water heating units. Magnesium rods are not recommended to be used in homes with hard water as they will corrode quickly, reducing the effectiveness of the anode rod to almost nothing in a very short time.

If you live in an area that has hard water and your water heater has a magnesium anode rod, you should check your water heater lining to be sure it is not corroded. You should not install a magnesium anode rod in a corroded water heater tank as it could cause an electrochemical reaction that produces hydrogen gas inside the tank. This can cause water leaks from the tank lining.

Insiders Tip: If you have a water softener system installed on your house, the magnesium anode rod is recommended because the sodium ions will attack the magnesium anode rod easier than the aluminum anode rods.

Aluminum Anode Rods

Aluminum anode rods were more commonly found in older water heaters. They are no longer commonly used due to the risk of metal poisoning in the hot tap water supply. This is the cheapest and longest-lasting type of anode rod available.

Aluminum anode rods can be easily identified because it is very flexible. Homes with very hard water problems may find they need to use aluminum rods because they corrode very slowly, providing greater protection for the tank.

Zinc Anode Rods

This type of anode rod is made of both zinc and aluminum. It is made up of one part zinc and 10 parts aluminum. Although it doesn’t come standard on most water heaters, it’s a great upgrade option particularly if you have hard water and a sulfur “rotten egg” smell coming from the water heater. Not only does it provide long-lasting protection for your tank, but it also controls the growth of bacteria which can cause that nasty ‘rotten egg’ or sulfur smell.

Combination Anode

The combination anode rod is a typical anode rod that is attached to the hot water outlet. Most water heaters do not have this setup as it’s difficult to access and service. The combination anode is installed inside the pipe which makes it hard to reach. Often times you have to break the pip to access and remove it for replacement.

Powered Anode Rods

Powered anode rods use electrical pulses to remove corrosive electrons from the water inside the tank and prevents it from attaching to the inner lining which will eventually rust the tank from the inside out causing it to leak. Powered anode rods are not sacrificial and do not require replacement.

However, they do require some routine cleaning to maintain an electrical charge. These anode rods are not found in residential water heaters when purchased. These are an after-market improvement that can virtually double the lifespan of your water heater.

Powered anode rods are particularly good for controlling smelly water. They do this by killing anaerobic bacteria in the water that leads to the water having a “rotten egg” smell.

Our pick for the best powered anode rod on the market today is Corro-Protec CP-R Water Heater Powered Titanium Anode Rod. This powered anode rod comes in 3 different sizes to fit the size of your water heater.

Powered vs Sacrificial Anode Rod – Which is Better?

A powered anode rod is well worth the cost, particularly if your water heater is newer and the inner lining of the tank is still in good condition. However, I do not recommend them for older water heaters. If your water heater anode rod has never been replaced, the inner lining has likely already started to corrode.

Anode rods need to be replaced every 3-5 years (less if you have very hard water). If your water heater is over 5 years old and when you check the anode rod you find it is completely corroded, you’re probably better off replacing the anode rod with a cheaper aluminum, magnesium, or zinc anode rod because you’ll likely need to replace the tank in the next 3-5 years regardless.

What are the Different Sizes of Anode Rods?

Magnesium anode rods are straight. They are usually around 33 inches long with a ¾ inch diameter.

Aluminum anode rods are also about 33 inches long with a ¾ inch diameter. They can bend at the 2 joint areas, making them more adaptable.

Zinc anode rods are also straight and a bit longer than magnesium rods, about 44 inches in length with a diameter or ¾ inch. They can be easily cut to fit different size heaters and dissolve more completely than pure aluminum rods.

Can You Cut an Anode Rod?

Yes, you can cut an anode rod to fit your specific water heating unit. All you need is a hacksaw and a file, to smooth the cut edges. You could consider using a flexible anode rod or simply bending rather than cutting it.

You will not need to cut a powered anode rod. These can be purchased in 3 different lengths to fit the size water heater you have.

How to Cut an Anode Rod?

If you have an anode rod that doesn’t fit your water heater perfectly, you can cut it down. The correct way to do this is to place it into the water heater (without screwing it in) so you can see how high it is. Then, measure the distance that the rod is protruding out of the top of the tank and add an extra inch. Use a hacksaw to cut the excess off and then place the rod back in the tank. Screw it into place and you’re done!

How Often Should You Change Anode Rods in Water Heaters?

Water heater anode rods should be changed approximately once every 3 to 5 years, provided that the unit is functioning properly. If you live in an area with extremely hard water and a higher composition of calcium and magnesium minerals, then you may need to change it more frequently, around once every 3 years or so. The quality of the water is the true determining factor here. 

It’s worth mentioning here that investing in a water softener will also help keep your storage tank running smoothly, thus reducing the number of anode rod changes required. A water softener significantly reduces calcium and limescale build-up that, over time, can affect not only your heating unit but also damage your taps, pipes and other water fixtures.

What is the Best Anode Rod?

Buying the right anode rod can be tricky. There are so many different brands and styles available to choose from. A good one to consider that is available online through Amazon.com is the About Fluid Aluminum/Zinc Flexible Anode Rod Complete Kit. It comes with everything you need, including step-by-step, easy-to-follow instructions and is guaranteed to fit almost all water heating units!

This anode rod ‘wins the war on smelly water’ by eliminating hydrogen sulfide gas that gives off a yucky, rotten egg smell! It can be installed in even the smallest spaces and, best of all, preserves your tank while saving you money!

How to Replace the Anode Rod in Your Water Heater

Insider’s Note: the directions below are for most models of water heaters. However, if you have a Bradford White water heater or another brand that has an anode rod located on the hot water outlet, replacement can be difficult. As you’ll see in the video above, replacement of these anode rods can be tricky. If you are unsure you can complete the job, you should contact a licensed plumber for assistance.

What you’ll need:

  • A second person to help you
  • 1-1/16″ Socket 
  • Garden hose
  • Bucket
  • Teflon tape
  • Plumbers Pipe Dope
  • New anode rod
  • New hot water outlet nipple (for anode rods connected to the hot water outlet only)

If you have a top mounted anode rod, I recommend the About Fluid Aluminum/Zinc Flexible Anode Rod Complete Kit found on Amazon. I used this kit to replace the anode rod in my water heater. It comes with or without the 1-1/16″ socket.

Prep Steps

Look at your data tag to determine the model number of your water heater. Using a Google search type in “anode rod ‘water heater brand and model number'”. If you have a hot water outlet connected anode rod, you’ll likely damage the nipple taking it out so plan to purchase a new one. Another good resource is Plumbingsupply.com

Turn off the power or fuel supply

Before you begin working on the water heater you’ll need to turn off the power supply. If you have a gas water heater simply turn the thermostat to the vacation or pilot setting. For electric water heaters, you’ll need to turn off the breaker located inside the electrical panel box.

Turn off the water supply 

You’ll need to locate and turn off the cold water supply coming into the water heater. The cold water supply should be within reach of the water heater on the cold water supply pipe.

Drain the water heater

You’ll need to drain a minimum of 10% of the water from the tank. You’ll need to connect a garden hose to the drain valve at the bottom of the water heater and direct the garden hose into a bucket, floor drain or to the exterior of the home. 

You’ll need to open the hot water tap on the nearby sink and then open the drain valve to allow water to drain from the water heater.

Now you only need to drain a little bit of water to change the anode rod. You’ll need the weight of the water inside the tank to help hold the water heater in place.

Upon completion of the water heater draining, close the drain valve and remove the garden hose. We will address the open hot water tap and the cold water supply shut off in a later step.

Locate and Remove the Anode Rod

The anode rod is located on the top of the water heater. You can identify it by the hex head bolt top. You’ll need a 1-1/16 inch socket to remove the anode rod. As stated earlier, some anode rods are connected to the hot water outlet. If this is the case, you’ll need to disconnect the hot water supply to access the anode rod for replacement.

  • Removing the anode rod is a two-person job. It’s a good idea to have someone help hold the water heater tank (especially if it’s drained) to keep the water heater from shifting and breaking the supply pipes. 
  • If your water heater is located in an area with limited height clearance, you may need to bend the anode rod in order to remove it.
  • Never hit or hammer the tank to remove the anode rod as this could damage the inner tank causing it to leak.
  • If you are having difficulty removing the anode rod, try using a breaker bar to break the rusted seal. I do not recommend using lubricates like Liquid Wrench or WD40 as they could leak into the water heater and contaminate the water supply. Apply firm pressure and slowly twist to loosen the anode rod.
  • Once loosened, pull out and examine the anode rod to determine if a replacement is needed. If the anode rod still has its full length and is only lightly corroded, the anode rod is still functional and you can reinstall it. Be sure to apply new Teflon tape and pipe dope to the threaded end of the anode rod before reinstalling it to create a watertight seal. 

Install the New Anode Rod

After you remove the old anode rod you’ll need to install the new anode rod. If you have a limited height clearance over the water heater, you may need to install a flexible anode rod instead of a solid one.

Apply Teflon tape to the threaded end of the anode rod. Secured the anode rod with the 1-1/16 inch socket. Reconnect the hot water outlet piping if needed.

Turn on the Water Supply

Once the anode rod is installed it’s time to turn the cold water supply back on to refill the water heater.

Once the water heater tank has refilled and water is passing through the open hot water tap, close the hot water tap. 

Turn on the Power/Fuel Source

Restore power back to the water heater. For gas water heaters to set your thermostat back to the on position and adjust to the temperature of your choosing. For electric water heaters turn the breaker back on at the electrical panel box.

Allow approximately one hour for the water heater to recover. Periodically check the anode rod connection to be sure it is not leaking. If leaking is observed tighten the connection with your 1-1/16 inch socket. 

Conclusion

To conclude, the anode rod is the single most important component of your water heaters’ longevity. It protects your water heater from rusting out and leaking from the bottom of the tank. Whether you choose a standard anode rod or a powered anode rod, by servicing your water heater and replacing your anode rod as needed, your water heater will last for many years to come.

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Hubert Miles

I've been conducting home inspections for 17 years. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and FHA 203k Consultant. I started HomeInspectionInsider.com to help people better understand the home inspection process and answer questions about homeownership and home maintenance.

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