Extend the Life of Your Water Heater by Replacing the Anode Rod

Remove the old rod

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Crank out the old rod

Turn the hex head of the old rod counterclockwise to unscrew it. Pull it out and screw in the new rod.

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New vs. used

Anode rods are designed to attract corrosive elements in the water, thereby diminishing corrosion in the vulnerable steel liner.

Most water heater tanks are steel with a thin glass lining to protect the metal from corrosion. Since the lining eventually cracks, tanks have a second line of defense against rust: a long metal “anode rod” that attracts corrosive elements in the water. When the rod itself becomes so corroded that it can no longer do its job, the tank soon rusts out, leaks and needs replacement. However, if you replace your anode rod before it fails, about every five years, you can double the life of your water heater.

Rods are made from magnesium, aluminum or aluminum/zinc alloy. Aluminum replacement rods are sold at home centers. In most cases, the hexagonal head of the rod is visible on the top of the water heater. If you don't see the hex head, check your owner's manual. The rod may be under the water heater's sheet metal top or connected to the hot water outlet nipple. (A few newer plastic-lined tanks have no anode rods to replace.)

Before you get started, close the shutoff valve, turn on the hot water at a faucet to relieve pressure, and turn off the electricity or gas to the heater. Open the drain valve near the bottom of the tank and drain out about 2 gallons of water. Caution: The water is hot!

If the hex head is set below the top of the heater, you'll need a 1-1/16-in. socket to reach it. If it protrudes above the top, you can use any type of wrench. Chances are your old anode rod will be frozen in place by corrosion. Douse the head with a spray lubricant such as WD-40 and give it a few minutes to penetrate. You may also have to slip a “cheater” pipe over the wrench handle to increase your torque. The weight of the water in the tank is usually enough to keep the entire heater from turning. But if it begins to move, have a helper (or two) hold it in place.

When the threads break free, stop turning and look for water around the hex head. If you see leakage, drain the tank further. If you don't have enough overhead clearance to pull the rod out of the tank, bend it as you remove it. Then when you buy a new rod, choose a flexible, “segmented” version. Smear Teflon pipe thread sealant on the threads of the new rod before you install it. Don't use tape, since it can reduce the effectiveness of the rod. Before you turn on the water and electricity or gas, drain another gallon out of the tank to flush out any remaining debris.