Water Heater Anode Rod: The Cheap Part That Protects Your Tank

The anode rod is the inexpensive part that keeps a tank water heater from rusting through. It is a metal rod of magnesium, aluminum, or an aluminum-zinc composite that hangs down into the tank from the top. The water corrodes the rod instead of the steel tank, which is why makers call it "sacrificial." A.O. Smith says that once the rod is used up, the tank starts to corrode and eventually leaks, and that replacing the rod before it is gone can add years to the tank's life. Check it once a year, as A.O. Smith and Rheem recommend, and replace it when it is worn down to its core wire.

Checking it means turning off the heat and water, draining a few gallons, and unscrewing the rod with a 1-1/16-inch socket. A stuck rod, a low ceiling, an anode built into the hot water outlet, or a tank that already leaks makes it a plumber's job.

What the Anode Rod Does

Most tank water heaters, gas and electric, have at least one anode rod. A.O. Smith explains that the difference between the rod's metal and the tank's sets up a natural electrical current, the principle a battery uses, and that current controls corrosion of the tank. A.O. Smith says a rod's life depends on the chemicals in your water, how much hot water you use, and whether you have a softener, and that rods usually last 3 to 5 years.

When to Check or Replace It

1. It has been a year. A.O. Smith and Rheem say to inspect it annually, and A.O. Smith adds a professional inspection every 5 years. Bradford White's electric manual says every 2 years.
2. The rod is 3 to 5 years old, or you don't know. That is A.O. Smith's typical life for a rod.
3. Rust-colored hot water. A.O. Smith says it suggests the anode is used up and the tank may be failing; Rheem says brown or reddish water often points to tank corrosion or a deteriorating anode.
4. A rotten-egg smell from the hot taps. A.O. Smith says it usually comes from bacteria reacting with the anode. The makers' fix is a different type of anode plus disinfecting the tank; see hot water smells like rotten eggs.
5. Sputtering, cloudy, or discolored hot water, which Bradford White says can mean the water needs testing or the anode material needs changing, or jelly-like beads when you flush, which A.O. Smith says come from an aluminum anode.
6. A water softener, which A.O. Smith and Bradford White say uses the anode up faster; check it more often.

What a worn rod looks like

A.O. Smith says a healthy rod is smooth and about half an inch thick; replace it if it shows deterioration or several inches of bare core wire. Rheem says to replace it when more than 6 inches of core wire shows at either end, or when it is corroded, thinned, or coated with calcium or sediment.

Magnesium vs. Aluminum vs. Powered: What Each Anode Is For

The type matters most when you have a water softener or a smell.

With a smell, A.O. Smith and Bradford White pair the new anode with disinfecting the tank, and A.O. Smith says a special anode may reduce but not eliminate odor. For an alternative anode, Bradford White points you to the supplier that installed the heater.

What You Need

• The right replacement anode for your model. Bradford White says to ask the installing plumber or the manufacturer on the rating plate, and A.O. Smith's electric warranty requires a factory-approved rod.
• A 1-1/16-inch socket (A.O. Smith and State both specify it) and a ratchet or breaker bar. Corro-Protec says a 6-point socket grips better than a 12-point and is less likely to strip the head.
• Teflon tape or approved pipe sealant for the threads, per A.O. Smith and State.
• A garden hose, bucket, towels, gloves, and goggles.
• Headroom. The rod comes out straight up, and one A.O. Smith gas manual says it could be as long as 35 inches. If space is short, A.O. Smith says to pull part of the rod up, cut it off, and repeat; Corro-Protec warns not to drop pieces into the tank. For the new rod, A.O. Smith suggests a segmented anode in tight spaces. These are built to flex: anode maker Water Connection says its 44-inch segmented rod needs only 12 inches of clearance.

How to Check and Replace the Anode Rod, Step by Step

These steps follow A.O. Smith's and State's anode procedures; where your manual differs, follow it.

1. Turn off the heat. Electric: switch off the breaker, or both breakers if there are two. Gas: turn the control knob to Off and close the gas shutoff valve on the supply pipe, and turn off any power cord or switch. Ideally do this a few hours ahead so the water cools.
2. Close the cold water supply valve. Rheem says to make sure the cold supply is off before removing the anode.
3. Relieve the pressure. Open a nearby hot faucet and leave it open; State says this depressurizes the tank.
4. Drain a few gallons. Run a hose from the drain valve to a floor drain or outdoors and let out about 5 gallons, as A.O. Smith's anode procedure directs, then close the valve. The flush guide covers the drain valve.
5. Find the anode. Look on top for a hex head, often under a plastic cap; on at least one A.O. Smith model, foam under the cap has to be chipped away. Bradford White's manuals describe a combined anode and hot water outlet nipple, which is part of the plumbing. Your manual's parts diagram shows yours.
6. Brace the heater and loosen the rod counterclockwise. For a stubborn rod, Corro-Protec suggests strapping the heater so it can't turn, a breaker bar, then an impact wrench. If the tank or pipes start to twist, stop and call a plumber.
7. Pull it out and inspect it, cutting it into sections if the ceiling is low. A rod that is still smooth and thick can go back in with fresh sealant; a cut one has to be replaced.
8. Install the new rod. Wrap the threads with Teflon tape or coat them with approved sealant, start the rod by hand, then tighten it with the socket until it is watertight.
9. Refill completely before restoring the heat. Make sure the drain valve is closed, open the cold supply, and leave the hot faucet running until the flow is steady with no air; State says to keep it running 3 minutes more. On an electric heater this is essential: A.O. Smith says that without enough water around the element, it will short out and be destroyed, and Bradford White says elements fail completely if they aren't fully under water.
10. Check for leaks, then turn the heat back on. Close the faucet and look for drips at the anode fitting; State says to fix any before going further. Then switch the breaker on, or relight a gas heater by the instructions on its label.

When to Call a Plumber

• The rod won't come out, the hex is rounding off, or you lack the tools or headroom. Rheem says anode replacement often requires tools and safety precautions best handled by a qualified plumber.
• The tank already leaks. A new anode won't fix it: A.O. Smith says a leak from the base may mean a corroded tank, usually more practical to replace than repair. Shut it down and see water heater leaking.
• The heater is old. A.O. Smith puts tank life at 8 to 12 years, and Rheem says to plan a replacement around 10. Ask a plumber whether a new anode is still worth it.
• The anode is in the hot water outlet, or is powered and wired to the controls. State's service handbook, which covers its powered anodes, is written for licensed plumbing professionals.
• Warranty questions, and anything on the gas side: the valve, burner, or venting.

The Anode and Your Warranty

Never run the heater without an anode. A.O. Smith: "Do not remove the anode leaving the tank unprotected. By doing so, all warranty on the water heater tank is voided." Rheem and Bradford White say the same, and Rheem adds that it greatly shortens the tank's life. Replacing it is normal maintenance, but A.O. Smith's electric warranty applies only with factory-approved anodes installed, and Rheem says some work must be done by a licensed technician to keep a warranty valid, so check your manual first.

Relief Valve and Temperature

Never cap, plug, or thread the T&P relief valve's discharge pipe; A.O. Smith, Bradford White, and Rheem all prohibit it. When the heater is back on, keep it at 120°F, the setting the CPSC urges to prevent scalds and the one A.O. Smith's electric thermostats are factory set to. Even at 120°F, the CPSC says, five minutes of exposure can cause third-degree burns.

Frequently Asked Questions

Can I take the anode out to stop a rotten-egg smell?

No. A.O. Smith, Rheem, and Bradford White all say that voids the tank warranty. The makers' fix is a different anode (aluminum, aluminum-zinc, or powered) plus disinfecting the tank.

Do electric water heaters have an anode rod?

Yes. A.O. Smith's electric manual says each heater has at least one. The steps are the same, but refilling before the power goes on matters most, because the elements burn out without water around them.

Does the warranty cover a new anode?

Not at A.O. Smith, whose gas manual calls anode rods a consumable item not covered under warranty. Treat the rod as routine maintenance, like the yearly flush.

The Bottom Line

The anode rod corrodes so your tank doesn't. Check it yearly, more often with a softener, and replace it when it is worn to its core wire. Work with the power or gas off, the cold supply closed, the pressure relieved, and a few gallons drained, and refill completely before the heat goes back on. Never run without an anode, and never cap the relief valve. A stuck rod, a low ceiling, a hot-outlet anode, or an old or leaking tank is a plumber's job.

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