Water Heater Anode Rods 101: What They Are, Types & How They Work
Last Updated: 1 March 2026
***DISCLAIMER: PLEASE REFER TO YOUR MANUFACTURER’S INSTALLATION MANUAL FOR INFORMATION REGARDING YOUR SPECIFIC MODEL. IF YOU ARE ATTEMPTING TO SERVICE YOUR OWN HEATER, PLEASE DO SO WITH CAUTION; U.S. WATER HEATING SOLUTIONS, LLC. AND THE OTHER ORGANIZATIONS MENTIONED BELOW ARE NOT RESPONSIBLE FOR ASSOCIATED LIABILITIES. THIS ARTICLE IS MEANT TO PROVIDE AN INFORMATIVE AND EDUCATIONAL SUMMARY AND DOES NOT SUPERSEDE OFFICIAL WATER HEATER REPAIRS OR MANUFACTURER INFORMATION.
What is an Anode Rod?
An anode rod is a metal rod, usually with a hexagonal head (hex head) and a steel wire on the inside. This part screws into the top of a water heater. Anode rods are made of magnesium, aluminum, or zinc-aluminum alloy.
What is the purpose of an Anode Rod?
Anode Rods prolong the life of your water heater by preventing corrosion via electrolysis.Water contains various bacteria and minerals, depending on its source. Bacteria can cause water to smell, while minerals like calcium and magnesium contribute to corrosion inside the tank. If your home is located in a rural area or an area where excess non-harmful bacteria and minerals are present in the water supply, you may have hard water. With the tank constantly expanding and contracting as the water is heated, the tank and its lining are being put under stress. Over time, the stress can result in cracks in the lining that enable the bacteria and minerals from the hard water to reach the metal of the tank, increasing the chances of a leak. The anode rod attempts to decrease some of this possible corrosion.
Examples of Anode Rod Locations
Where is the Anode Rod located?
The anode rod is usually located slightly off-center in most water heaters. For residential water heaters, most will be located on the left side near the outgoing hot water, but some models may have their anode rods on the right side, near the incoming cold water; the anode rod typically has a plastic cover on top and may be accessed from the top of the unit. For commercial water heaters, the location of the anode rod(s) varies by manufacturer, but most are also found on the top of the unit with the exception being some Rheem Triton water heaters whose anode rods are on the front of the unit.
The image slider in this article shows the location of the anode rod on a residential electric water heater and how the anode rod cover is labeled with "ANODE." There are also examples of commercial water heaters shown.
Do ALL water heaters have an Anode Rod?
ALL traditional tank type water heaters have an anode rod, regardless of whether they are electric, natural gas, LP gas, hybrid heat pump , or solar powered.
Tankless water heaters DO NOT have anode rods because they heat the water on demand, while traditional tank type water heaters store the heated water.
Can there be more than one anode rod?
Residential water heaters usually have one anode rod and commercial water heaters tend to have two anode rods, although this varies by the manufacturer and model. Some commercial water heaters may have three or more anode rods each. For example, Bradford White EF units have a total of four anode rods: 1 powered anode rod and 3 magnesium anode rods.
How Often Should an Anode Rod Be Checked?
Anode Rods should be checked on an annual basis. Manufacturers often recommend a minimum annual anode rod check as part of annual
preventative maintenance, but heaters operating on well water will likely need more frequent checks (semi-annually or quarterly).
How Do I Know When to Change My Anode Rod?
Anode Rods with noticeable sediment build-up and/or corrosion should be changed, especially if your anode rod is corroded down to the steel wire. Sediment build up on the anode will be easily noticeable, just as it is on an element. Additional signs your water heater may have sediment build up include: rumbling, cracking, and popping sounds coming from the tank.
If you have an electric heater and you notice sediment/corrosion on your anode rod, you may also want to consider having the elements checked and possibly replaced. See above for an example of the stages of anode rod depletion.
Types of Anode Rods
There are several different types of anode rods: the traditional style rods, flexible anode rods, and powered anode rods. Here's a short summary of the differences:
- Traditional Style Anode Rods: These anode rods include a metal wire with a rod made of magnesium, zinc, or zinc-aluminum. They are sacrificial anode rods, meaning they will deteriorate over time, as they help decrease the risk of corrosion in the water heater.
- Flexible Anode Rods: Similar to traditional style anode rods, these rods include a metal wire with a rod made of magnesium, zinc, or zinc-aluminum. However, the difference is that unlike the traditional rods, they are composed of three small rods with flexible wires between them (almost like sausage links). They are useful for replacing anode rods located in tight spaces, where there is limited room above the water heater.
- Powered Anode Rods: These anode rods may also be known as electric anode rods or electronic anode rods. They are rather standard for commercial water heaters and are a common upgrade for residential water heaters. Unlike traditional rods, these are powered by electricity and have a significantly longer life expectancy, with some anode rod manufacturers offering generous warranties.
Can Anode Rods Fix Smelly Water?
Smelly water is typically caused by the origin of the water and/or a chemical reaction with the bacteria. Sulfur is another common mineral found in water, often responsible for causing a rotten egg smell. This can sometimes be amplified by interactions between hard water and magnesium anode rods.
A.O. Smith recommends several fixes for smelly water:
- increasing the temperature on the gas control valve or thermostat above 140 degrees (recommended temperature setting is 150 degrees)
- NOTE: Please be aware of scald risk
- installing mixing valves at each point of use to kill any bacteria; engaging in a chlorine treatment
- changing the anode rod from magnesium or aluminum to one made of zinc-aluminum alloy.
- In some cases, using the wrong anode rod in certain types of water can result in a chemical reaction, where non-harmful sulfur reducing bacteria produce smelly water
One of the commonly used zinc-aluminum anode rods our technicians install is an A.O. Smith KA-90 Anode Rod (100108571). This type of anode has helped many of our well water-based customers rid their homes of the smelly water.
How do I know if I have hard water?
Knowing if you have hard water is important because it can affect your water heater and your well being. One of the most general symptoms of hard water is the presence of white water stains. If you washes dishes and leave them out to dry, do you notice white stains? Do your shower walls have an unusual coating that is not from soap or cleaning products? Do you dislike the way your water feels when you shower? If yes, you may have hard water.
You can easily determine whether you have hard water by performing a PH Test on water samples from your home. When you dip the test strip into the water, your result should read around a 7. If your strip does not match the green/neutral area on the test kit chart, you likely have hard water [Example Test Strip Kit]. If you are concerned about your water quality, we strongly recommend having a water sample analysis performed by a trustworthy lab to get a better picture of your water's quality.
You can also find additional guidelines for different types of water testing, as hard water is not the only concern regarding potable water supply.
Can Anode Rods be Replaced?
Yes, most water heaters' anode rods can be replaced.* The replacement process will first require you a technician to locate the anode rod on the top of the unit. The technician will then partially drain the water below the anode rod. The technician will then unscrew and remove the old anode rod, which will likely show signs of corrosion. In some rare cases, the amount of build-up around the threading of the anode rod may prevent anode rod replacement. The technician will also need some headspace above the heater to clear the old anode rod's removal and to insert the new one. If you do not have sufficient space for the new traditional style anode rod, you may opt for a flexible anode rod such as the A.O. Smith
100110784 (Magnesium Flex Anode Rod) or 100110627 (Aluminum Flex Anode Rod). Although there is a large variety of anode rods across the major manufacturers, our technicians all carry the
A.O. Smith KA-90 Anode Rod (100108571) as part of their regular truck stock and we also have a small stock of the Magnesium Flex Anode Rods in our warehouse.
*Which water heaters DO NOT have replaceable Anode Rods?
Some direct vent water heater models (usually made specifically for mobile homes or manufactured housing) do NOT have removable anode rods. You can find this information in your water heater's manual or by contacting the manufacturer's technical support.
Although we do not yet have an exhaustive list of all the models this applies to, we know these models may be effected:
- Rheem Model# 22DV50F
- Rheem Model# 24I40FDVX
Why can't some direct vent water heaters' anode rods be replaced?
This is the result of the way these water heaters were designed. The anode rod is not easily accessible, often located within the heater's top pan and below several inches of foam insulation. It is against the manufacturer's recommendation to remove the top pan and/or cut out the foam installation to remove the water heater, as this may impact the heater's regular operations,
void your warranty, and be difficult to re-assemble.
What should I do if I can't replace the anode rod in my direct vent water heater?
If you have a direct vent water heater with an anode rod that is not serviceable due to its location, it cannot be replaced. As long as you are not experiencing any issues, you should continue performing annual maintenance. However, if you are experiencing other issues like smelly water, the manufacturer will recommend the following:
- Keeping up with annual maintenance (or more frequent maintenance)
- NOTE: water quality issues won't be resolved by annual maintenance, but it can help alleviate the issue for some time
- Investing in water softener/water treatment
- Having well system and well pump serviced
- Turning up the temperature on the water heater to 140 degrees or higher to kill the bacteria
- NOTE: BE AWARE OF SCALD RISK IF YOU CHOOSE THIS OPTION
- Water Heater Replacement: Depending on the age of the heater and severity of the anode rod issue, it may be time to replace the heater with an option that has an serviceable anode rod. This should be a last resort option, as it is among the most expensive options. ***Be sure to check the online manual BEFORE purchasing the new heater so that you know if the anode rod is replaceable***
Will Anode Rod Replacement be Covered by the Manufacturer's Warranty?
In most cases, anode rod replacement will not be covered by the manufacturer's warranty. Anode rod deterioration is considered part of normal wear and tear that is caused by use of the water heater and/or water quality, which are considered external to the warranty as it is meant to cover manufacturing defects.
Here are some samples from manufacturer's warranties about anode rods NOT being covered:
- A.O. Smith: "Anode rods are consumable maintenance parts and are excluded from warranty coverage" (Source: A.O. Smith Limited Warranty Sheet)
- Bradford White: "What does this limited warranty not cover? | c) Adverse local conditions, and specifically, sediment or lime precipitate in the tank or corrosive elements in the atmosphere. d) Misuse, and specifically, operation, and maintenance contrary to the written instructions furnished with the unit, removal of magnesium anode, disconnection, alteration or addition of non-approved components or apparatus, operation with fuels or at settings other than those set forth on the rating plate or accidental or other exterior damage" (Source: Bradford White Limited Warranty Sheet)
- Rheem/Richmond/Ruud: "Warranty Exclusions | This limited warranty will NOT cover: c) Damages, malfunctions, or failures resulting from improper installation or failure to operate and maintain the water heater in accordance with the manufacturer’s instructions provided; f) Damages, malfunctions, or failures caused by operating the water heater with the anode rod removed or with modified, altered, or unapproved parts installed" (Source: Rheem Limited Warranty Sheet)
There may, however, be some exceptions where a manufacturer will cover anode rods under warranty:
- Anode rod missing in a new water heater
- Anode rod incorrectly installed at factory
What if I want to replace the Anode Rod and it breaks?
If you are replacing the anode rod, it is likely because it is corroded. That being said, you may have difficulty removing the anode rod if it is extremely corroded. If the anode rod breaks during removal, you will not be able to remove the portion that breaks off. Instead, it will fall to the bottom of the tank.
Are Anode Rods universal? Do I have to use the exact part number listed for my unit?
No, anode rods are not universal. In general, they tend to have a 3/4" NPT hex head threading and length from 40-55" for the traditional style rods.
Although not all anode rods are made the same, you can upgrade the material of the anode rod or upgrade to a powered anode rod. If you are looking to upgrade the material from one type to another, you can either match up the 3/4" NPT hex head threading measurement in the description of your unit's original anode rod with the length measurements, where the only difference is the material. You may also contact the manufacturer's technical support for their best recommendation. Alternatively, many anode rods can be used across different water heater brands. Make sure the the replacement has 3/4" NPT threading the same as the original and that the replacement is close in length; the replacement's length should be the same as the original or slightly longer so that it can be cut down to size, but it should not be shorter.
If you are looking to upgrade to a powered anode rod, it is best to follow the anode rod manufacturer's guidelines.
What should I be aware of before attempting to replace an anode rod?
- The Anode Rod's Size and Overhead Clearance Space: If you are replacing an old anode rod that may be corroded, it may be easier to removed because you will likely only have a portion of the rod itself left and the hex head or possibly even the hex head alone. However, when you replace the anode rod with a brand new one, it will likely be between 4 feet and 5 feet long, which means you or a service technician will have to stand over the top of the heater and will need significant space between the heater and the ceiling to be able to replace the anode rod. If you have limited space, you may opt for a smaller electric anode rod like the Corro Protec or a flexible anode rod.
- Electrical Outlet Accessibility for Upgrading to Powered Anodes: If you are upgrading your residential water heater's anode rod from a traditional or flexible rod to a powered anode rod, be sure you have an accessible outlet nearby that can be dedicated to the electric anode rod before purchase.
- The Required Tools: To remove the anode rode and tighten the replacement, you will need a socket wrench with an extension. The 1-1/16" socket wrench is usually required across all manufacturers.
Purchase a Replacement Anode Rod from U.S. Water Heating Solutions
U.S. Water Heating Solutions stocks a small variety of genuine replacement anode rods for commercial and residential water heaters.
Our Parts Dept. experts are happy to assist you in determining which anode rod your water heater needs; please be sure to have your model and serial number handy so that we can verify replacement anode rod compatibility with your water heater.
How Much Does an Anode Rod Cost?
Standard anode rods tend to cost anywhere from $50-$150, averaging about $75 each. Powered anode rods (a.k.a. electric anode rods) are usually more expensive and can cost upwards of $150-$300 for residential water heaters and over $500 apiece for commercial water heaters.
How Much Does Anode Rod Replacement Cost?
Although the cost of anode rod replacement varies by region and installation circumstances, here are some of the most important factors that service providers will consider in their pricing:
- Are you replacing your anode rod with one of the exact same type or is it a different material? (This affects the price of the replacement anode rod, especially if you are upgrading to a powered anode, which tend to be more expensive)
- Do you have sufficient space to remove the anode rod? (This may limit your options to flexible anode rods or powered anode rods, as well as add additional labor if it is difficult to remove the existing anode rod)
If you are contacting a service provider to change your anode rod, you may be able to save some money on labor costs by partially draining the tank yourself (connecting a hose to the drain valve, placing the loose end in a drain, then opening the drain valve) and then having a technician install the anode rod; it will be important to mention that you will have the tank drained ahead of time.
At U.S. Water Heating Solutions, we typically charge between $300.00 (standard anode rods) and $450.00 (powered anode rods) for residential anode rod replacement, including the cost of the new anode rod and labor for installation. We also offer lower rates for combined services (like maintenance and anode rod upgrades).
Purchase an Anode Rod Online from U.S. Water Heating Solutions:
*NOTE: Please be sure to check that the anode rod is compatible with your unit prior to purchase using your model and serial number.
We typically have the following anode rods in stock for online purchase or in-person purchase in Arlington Heights, IL:
- 100108571 | KA-90 Zinc Aluminum Anode Rod 42 in, 3/4 in NPT, 0.75 in [A.O. Smith]
- 100110784 | 9005973005 | Flexible Anode Rod 48 in, 3/4 in NPT [A.O. Smith]
- 100111023 | Shielded Powered Anode, 0.118 DIA x 48 [A.O. Smith]
- 100111024 |Shielded Powered Anode, 0.118 DIA x 13 [A.O. Smith]
- 100111286 | Shielded Powered Anode, 0.118 DIA x 31 [A.O. Smith]
- 100187890 | Powered Anode, 19.69 in [A.O. Smith]
- 100210012 | 9009087005 | Powered Anode, 0.118 DIA x 7.87 [A.O. Smith]
- SP11309C | Magnesium Anode Rod - 0.750 DIA x 44-3/8 in. long [Rheem]
- SP11309T | Magnesium Anode Rod - 0.750 DIA x 39.375 in. [Rheem]
- SP11526C | Magnesium Anode Rod - 0.900 DIA x 44-3/8 in. long [Rheem]
If your water heater anode rod is not listed above, please contact our Parts Dept. via our Contact Form or by phone for additional assistance.
Anode Rod Diagnosis & Replacement
U.S. Water Heating Solutions offers an array of water heater anode rod and general water heater services. Our technicians even stock a selection of the most commonly replaced water heater parts, including a small selection of anode rods on their service vans.
Common Anode Rod-related Water Heater Services:
- Anode rod replacement (part and installation)
- Water heater diagnosis & repair
- Water heater preventative maintenance
- Water softener installation
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