Water Heater Maintenance: The Sacrificial Anode

For most homeowners, a hot water heater is a forgettable device – that is, until it stops working or starts making noises! Most homeowners don’t do regular hot water heater maintenance, and as a result, they shorten the lifespan of the tank by half or more!

Conventional wisdom says that when the hot water tank starts making noises, it’s time to replace the tank. This advice has probably sold a lot of hot water heaters, but it’s not necessarily true. Your hot water tank may become noisy over time because sediment builds up in the tank. The sediment may be the result of minerals that occur naturally in the water, deterioration of the sacrificial anode, or deterioration of the tank itself.

In a hot water heater, a “sacrificial anode” is an exposed metal rod that is designed to corrode slowly over time. The sacrificial anode is made from magnesium, aluminum or a combination of zinc and aluminum. Water in the tank sets off an electrolytic reaction that would cause the exposed steel in the tank to fail quickly. To protect the steel, a more reactive aluminum or magnesium rod corrodes in its place. Once the sacrificial anode is corroded, the steel in the tank will begin to corrode, and the tank will fail.

To prevent the steel in the tank from failing, you should replace your sacrificial anode about once every three to five years, depending upon your hot water tank. Some tanks have longer warranty periods. Use the life of the warranty as a replacement guide for the anode. If you choose not to replace the sacrificial anode, the tank will keep working, but the steel will corrode and deteriorate. Tank replacement (and a big mess) is inevitable.

Sacrificial anodes typically screw into the tank, (often at the top) which makes them easier to replace. Note that sacrificial anode rods are long. You’ll need adequate clearance to remove them from the tank. If you don’t have 3.5-4 feet of clearance above your water heater, you may need to disconnect the tank to replace the anode(s).

Replace the sacrificial anode with one recommended by the tank’s maker. Aluminum anodes may be less expensive, but tend to corrode much more readily. This means you’ll replace the anode more often because more sediment will accumulate in the bottom of the tank. Aluminum anodes may also increase in diameter or break apart in chunks after they’ve been installed, so getting an aluminum anode out intact can be somewhat of a challenge! Cast-off aluminum can also be a source of noise in the tank. Finally, aluminum may contaminate the water. Hot water from the tap should not be used for drinking or cooking, and children should be cautioned not to put hot water from the tap into their mouths.

Some tanks employ two sacrificial anodes: a conventional rod (or two) at the top of the tank and an outlet anode at the top or bottom of the tank. All of the tank’s sacrificial anodes should be replaced at the same time and with the same metals. Don’t mix and match anodes! The cost of a replacement anode depends upon your hot water heater. Consult with us regarding replacement anodes. If you decide that the job is too big for you, we’re happy to inspect and replace your anode(s) for you.