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Water heater anode rod

Water heater maintenance and anodes

A water heater anode rod is the most important safety guard any storage tank has against corrosion and premature failure. With that said, most homeowners are both unaware and unfamiliar with anodes and how vital they are.

Periodically inspecting water heater anodes is the most overlooked maintenance procedure, this oversight alone is what causes most premature tank failures.

Inspecting the anode rod is not only important, it's essential. The condition of the anode will indicate whether or not corrosion is occurring within the storage tank.

Electric, Gas, Heat Pump and Solar Hot Water Heaters

If your considering, or recently purchased, a new energy efficient water heater (active solar water heaters included) keep in mind, how well the anode rod is maintained can almost single handedly determine the life span, not to mention both the energy efficiency and the cost effectiveness, of the purchased system.

Anodes and the basics

Water heating storage tanks come equipped with protective glass coatings, these coatings line the internal steel tank and protect the tank from corrosion and rust. But overtime these glass coatings can become susceptible to wear, caused mainly by storage tank sediment build up.

And even new tanks inevitably have flaws in the glass coatings that expose the internal steel lining. Manufacturers are well aware of this, that's why water heater anode rods are immersed in storage tanks.

Storage Tanks and Electrical Current

Within water heating storage tanks, small electrical currents are created by the dissolved minerals introduced to the water by way of the municipal supply. The current travels in the water and to all the surrounding metals that the water is in contact with. The electric current overtime corrodes these metals.

How Anodes Work

Anode rods are made of other metals other than steel, usually magnesium or aluminum, that react electro negatively in relation to the steel lining of the tank.

With the addition of a magnesium or aluminum water heater anode, the electric current travels from the water to the anode and to the other metal fixtures.

The anode protects the other metals in the tank, including the exposed copper fixtures, because magnesium and aluminum are scientifically less noble metals. 

So the current produces an electro chemical reaction that corrodes the anode rod before the more noble steel lining of the storage tank and the copper of the fixtures. This is why these anodes are commonly referred to as sacrificial rods.

These sacrificial rods are designed to absorb the corrosive electric current and deteriorate. But once the metal on a water heater anode is gone, the steel of the tank and the metallic fixtures will start to absorb the current and corrode.

Hex head and combination rods

Water heater anodes come in one of two different configurations; hex head rods and combination rods. Hex head rods are placed in separate ports along the top of the water heating storage tank.

In many older models, these anodes can sometimes be found under a layer of sheet metal. Combination rods, sometimes called outlet anodes, are combined with the tanks' hot water outlet tube.

Manufacturers have introduced tanks with two or more sacrificial anodes. More times than not a combination anode and one or more hex head anode are used. Since these tanks come equipped with more protection against corrosion, they generally come with longer lasting manufacturer product warranties as well.

Inspecting and replacing an anode rod

Sacrificial rods are designed to deteriorate overtime. Most water heating industry professionals recommend inspecting the anode about every 3 to 4 years. Home's with salty or softened water supplies should consider inspecting more frequently.

Warning, Always Exercise Caution

Please be advised that when servicing a water heater there's always the risk of scalding, and scalding is a serious health hazard even for healthy adults.

It's always a good idea to have additional towels and/or rags available when performing water heater maintenance tasks.

If you're uncomfortable or uncertain performing such water heater maintenance tasks on your own, consult with a local water heating professional. After all it's always better to be safe than sorry.

Locating the Anode Rod

If there are not three ports located at the top of the storage tank (one for the cold water inlet tube and one for the hot water outlet tube and another marked "anode" more times than not this indicates that the tank has a combination water heater anode. When in doubt consult a local water heating professional.

  • Turn off the power and the water supply to the water heater.
  • It's advised to drain the hot water heater, this ensures that heated water isn't present along the top.
  • Then locate the anode rod, some tanks may have the location stamped in the sheet metal along the top.
  • Unscrew the proper port fitting with caution. Water heater anode rods can be stubborn, especially on older tanks that have not been well maintained.
  • Carefully remove the old anode and compare it to the new one. If the old one has corroded to the point that it's diameter is less than half of the new one, replace it.
  • If a hard and thick calcium deposit has formed around the old rod, replace it.
  • Screw in the new water heater anode and remember to place pipe sealer or teflon tape to the thread of the nipple.
  • Turn the power and the water supply back on and remember to inspect the anode rod in the future. 

Magnesium Rods vs Aluminum Rods

Most storage tanks come with magnesium or aluminum water heater anodes. Many industry professionals prefer magnesium anodes mainly because they're known to produce a more driving current than aluminum.

Many throughout the water heating industry share in the conventional wisdom that because of this, magnesium rods are more effective at protecting the tank.

Aluminum water heater anode rods have also been known to collect corrosive sediments that can build up overtime, and in some instances the sediment can harden around the rod, making future inspection and removal challenging.

More on water heater maintenance

  • Water Heater Maintenance; how to extend the life of an old or recently purchased storage tank.
  • Drain Hot Water Heater; draining or flushing the storage tank removes sediments that can compromise efficiency and volume.
  • Water Heater Drain Valve; periodically inspect the drain valve on the tank for potential leaks and drips.
  • Water Heater Expansion Tank; high water pressure can compromise any storage tank. The addition of a hot water heater expansion tank can both resolve and prevent high water pressure.

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