Anode rod

What It Means

An anode rod is a long metal rod that hangs inside a tank water heater to protect the tank from corrosion. It's made of a metal that corrodes more easily than the tank's steel, usually magnesium, aluminum or zinc, so the water attacks the rod first and it wears away in the tank's place. That's why makers call it a sacrificial anode. Once the rod is used up, it can no longer protect the tank.

How It Sounds at Home

• "The plumber said the anode rod was down to the wire."
• "Have we ever changed the anode in this thing?"
• "It's the rod that rusts so the tank doesn't."

The Breakdown

How to check one, following the makers' guidance

1. Look up your heater's manual and model number. The steps for reaching the rod differ between models.
2. Turn off the electricity or gas and the cold water supplyMilk supplyHow much breast milk a parent's body makes. It's driven by supply and demand: the more often milk is removed, the more the body makes. See more, as the makers' drain steps describe, and give the water time to cool.
3. Take the rod out the way your manual shows. Stop and call a licensed plumber if it's stuck or you're unsure.
4. Compare it with the makers' signs. A rod in good shape is smooth and about half an inch across. Replace it if it's corroded, thinned, coated with calcium or sediment, or has several inches of bare core wire showing.
5. Put the old or new rod back as the manual shows, restore the water first and the power or gas last, and write down the date.

How often, per the makers. The pages range from a yearly inspection to at least every three years depending on local water, and every year if the home has a water softenerWater softenerA home system that removes the calcium and magnesium that make water hard, usually by trading them for sodium in a tank of resin beads. See more. One maker gives a replacement interval of every 3 to 4 years.

Try it today. Find your water heater's label, photograph the model number, and look up when the rod was last checked. If nobody knows, put a check on the calendar.

Good to Know

Working on a water heater means hot water, a tank under pressure and gas or electric power. Follow your own heater's manual, and call a licensed plumber if the rod won't come out, you're not sure what you're looking at, or the heater is gas and you aren't comfortable relighting it. Replacement rods come in different metals and lengths, so Buhata suggests matching the part your manual lists. The makers' maintenance guides list the anode check beside flushing the tank, which the water heater flushWater heater flushDraining a water heater and running water through it to wash out the sediment and minerals that settle inside, usually about once a year. See more page covers.

Related Terms and Categories

• Water heater flush

  Draining a water heater and running water through it to wash out the sediment and minerals that settle inside, usually about once a year.

• Tankless water heater

  A water heater with no storage tank that heats water as it flows through, only when a hot tap is on. Also called a demand-type or instantaneous water heater.

• Water softener

  A home system that removes the calcium and magnesium that make water hard, usually by trading them for sodium in a tank of resin beads.

• Appliance lifespan

  How many years a home appliance usually lasts before it needs replacing, from about 6 years for a compactor to 15 for a gas range in Consumer Reports' 2009 figures.

• Licensed contractor

  A contractor who holds the license your state or local government requires for the kind of work being done, which you can check before you hire.

Home maintenance and repairs