Water Heater Anode Rod
Installation and Replacement Tips

Extend the life of a water heater by replacing the deteriorated anode rod and before corrosion starts ruining the metal parts. Find out about the benefits of different rod types, problems, and solutions. A step-by-step guide on how to install and replace the anode.

What is an anode rod and how does it work

flexible anode rodA water heater anode rod, also known as the sacrificial anode, is the element that protects the metal tank from corrosion when in contact with the water (electrolyte). 

The anode is made of the steel core wire that is covered with one of three materials; aluminum, zinc or magnesium. As the anode has a higher current potential that other metal surfaces in the water heater, the galvanic current will flow from the rod to other metal parts, preventing the corrosion.

The water heater tank is usually constructed of steel, and the inside metal tank surface, as it is exposed to the aggressive water action, has a glass lining bonded to the steel for protection. As the lining could have or is subject to cracks, either due to the thermal and mechanical stress or imperfect manufacturing process, water can still get in touch with the metal tank, causing corrosion. This is why an anode rod is an important and integrated part of every design.

What is electrolysis

Electrolysis occurs when two metals are connected inside of water. The rod is more reactive and it will corrode before less reactive, which is the metal tank. It actually “sacrifices” itself to protect and extend the life of a tank.

Types of the anode rods

The anodes are located at the top of the water tank heater and are recognized by its hex-head plug end visible or hidden under the plastic cap.

The aluminum anode is recognized by the smooth surface on the plug. They are recommended in areas with hard water. These are the least expensive that usually corrode at a slower rate than other types. You can buy and install a straight or flexible type. Flexible aluminum anode rods are recommended where there is a limited vertical space, directly above the water heater. For the installation, just bend the flexible section and insert into the opening, section by section.

The magnesium anode has the weld bead on the plug. This type is the most used, especially where water is soft. It provides a good protection but it doesn’t last long.

The zinc or aluminum-zinc type is used where there is a high conductivity and due to the extremely hard water. These are providing an affordable solution for the rotten egg odor problem.

The powered anode is more expensive than the standard type but it effectively deals with the rotten egg smell. It is not sacrificial, but is permanent and provides a constant protection without losing its effectiveness over time. It plugs into the wall socket. You can buy it here.

How to test the anode rod

It is recommended to inspect the rod once a year to keep the tank safe from rust. The rod is submerged in the water and due to the aggressive water action is eaten away over time. If you find the rod depleted by 1/2 of its volume or more, it is time to replace it.

Anode rod problems and how to repair

The most common complaint related to the water heater anode rod is the rotten egg smell.

If you have a water softener installed, which is used to reduce the effects of the hard water resulting in mineral buildup within the tank, the soft water can significantly speed up the process of the anode depletion.

If you live in the area where the water supply has a high PH value (over eight) and there is an aluminum anode rod installed in the water heater, an excessive amount of aluminum hydroxide in a form of green, gray or blue "jelly beads" will form on the element.

If the iron bacteria, which causes the rusty hot water, is present in the heater, it might cause the premature rod failure.

Keep in mind that the process of deterioration depends on water conductivity. High conductivity increases the depletion rate.

How to replace/install the anode rod

Note: Keep in mind that the stored water inside the heater's tank might be hot.

Tools for the installation/replacement

  • Air compressor

  • Impact wrench

  • Socket wrench

  • Teflon tape

  • WD-40 (for stubborn anodes)

  • Garden hose or a bucket

Step-by-step guide

  • Turn OFF the water supply to the heater at the main shut-off valve located nearby the heater.

  • Turn OFF the gas and electrical supply. Turning the gas valve to OFF position is enough.

  • Use the garden hose and connect one end to the water heater drain valve and the other end to the open drain or outside. Drain a few gallons of water or below the outlet connection nipple.

  • Use the appropriate wrench to remove the anode rod (and the outlet nipple if the unit has one) from the heater. Use the 1-1/16 inch, 6-point socket tool to remove the rod.

  • Remove the rod from the heater.

  • It is normal to see signs of depletion on the rod, but if it is depleted over half of its original size, or if the steel core can be seen, replace it.

  • Once the new rod is installed, follow the steps from the above but in reverse order. Resume the operation using the instructions found on the label or manual.

We have heard that some homeowners have a hard time removing an anode rod, so they used oils or other solvents. Some plumbers use WD-40. This is not recommended because the solvents can get into the tank and pollute water.

A solution for the stubborn anodes can be an impact wrench, provide a lot of leverage by allowing a long lever on the wrench and tap with the hammer, and use the opposing wrenches and squeeze them.

As said before, periodic inspection and maintenance should be done at least once a year. The longevity of the water heater anode rod depends on several factors, and under normal conditions, you can expect it to last 3-5 years. If you prefer, you can buy a water heater, such as Rheem Marathon which does not use the anode, since the tank is made of plastic.

FAQ

Q: How often does the anode have to be checked?

A: It is recommended once a year.

Q: Where the anode is located on the tank type? 

A: It is located inside the body of the tank-type water heater and is screwed into the top.

Q: How do I know is the anode good or bad? 

A: Replace the rod if you see approximately 6 inches of the steel core or ½” of its volume is depleted.

Q: Can the water heater work without the anode? 

A: Yes, it can, but the metal parts will corrode faster.

Q: I use the water softener; does the soft water affect the anode? 

A: It can speed up the process of depletion.

Q: How often does the anode have to be changed? 

A: Recommendation is to replace it every 5-6 years under normal conditions, or if it got depleted to or more than the half of its volume.

Q: How much does it cost to replace an anode? 

A: It usually takes one hour so the price depends on how much does the technician charge (an hour in my town is $80). The price for the part is from $20 up.

Q: Why does my hot water smell like a rotten egg, or sulphur? 

A: The reason is the combination of the anode rod material and bacteria found in water.

Q: Anode rod is too long; can it be cut? 

A: Yes, you can use the hacksaw and cut it to the length you need.

Q: How can I install an anode if there is a limited space above the heater? 

A: Instead the straight, install the flexible one. Bend the anode at its flexible sections, one section at the time.

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