How To Extend the Life Of Your Water Heater — Change Water Heater Anode Rod

Stop rust before it happens.

Rust happens. Especially to steel-tank water heaters. Manufacturers take precautions to protect the water heater, but the best they can do is delay its inevitable demise. However, if you learn a little about how your water heater is built, and you take care of this one piece of maintenance, then you can extend the life of your heater and save yourself some dough.

The first thing manufacturers do in this battle of appliance versus corrosion is to apply a "glass" tank lining to keep water from reaching the steel tank. Really, this is vitrified porcelain. The application process is far from perfect, however, so most tank linings will harbor dozens of tiny pinholes. To keep these perforations from allowing water to rust the exposed steel beneath them, manufacturers install sacrificial anode rods through the top of the water heater tank.

Different metals corrode at different rates, which is key to understanding how these things work. Water-heater anodes are typically made of magnesium, and for some water conditions, aluminum. An anode rod is called sacrificial because it corrodes before steel does, saving your water heater's tank. (The actual chemistry involved here is quite complicated.)

There's no certain way to calculate how long an anode will last, but with fairly soft water, which attacks steel more aggressively than hard water does, five to ten years is a good bet. Probably the best indicator is the manufacturer's tank warranty. A heater with a six-year tank warranty is probably equipped with an anode that lasts about five years. A ten-year heater will be given a larger anode or even two. If it still has some life left in it, there's still no harm done replacing it.

One thing is certain: When a tank begins to leak, it's done. It can't be fixed. The trick is to replace a spent anode before the tank rusts out and leaks.

You'll find replacement anode rods at hardware stores and home centers ranging in price from $20 to $50. Most are around 40 inches long. You'll see some that are segmented so they can be bent. These are useful when you have short clearance above the heater.

To get started, kill the power if the water heater is electric. If the appliance is gas-fired, set the control valve to the pilot setting. Next, shut the cold water supply valve to the heater, and drain off two gallons of water. Now you're ready to start on the repair.

On the top of the water heater you should see a nut holding the anode in place. If you can't see it, look for a plastic cap, which will pry out easily to reveal it. Then, using 1-1/16 inch socket and breaker bar, back the rod out of the heater. Because this is a steel-on-steel threaded connection, you should expect some resistance. (It sometimes helps to have a buddy hold the heater by its hot and cold water pipes so it doesn't start to spin while you're doing this.)

When the nut breaks free, thread it loose and lift the spent rod from the heater (Photo 1). Install the new rod after applying a thin coating of pipe-joint compound to the first two threads of the nut (Photo 2). Don't overdo the compound, as a good metal-on-metal connection is needed for the anode to work properly. Now tighten the nut (Photo 3).

If you can't find a 1-1/16 nut at the top of the heater, then it is probably integrated with its cold water inlet fitting. If so, you'll need to cut the water inlet pipe above the heater and thread out the fitting, which is more work. The rest of the operation is the same, however.

Finally, for electric water heaters, restore power. For gas water heaters, turn the control valve from pilot to the temperature setting you used before. Open the cold water valve to the heater and replace the two gallons you drained off. Bleed out any air in the system by opening a hot-water faucet somewhere in the house. You're done, and you just added years to your water heater's life.

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