If you have always wondered what the small plug at the top of the water heater is, that is the hex head of the anode rod. An anode rod is a magnesium/zinc/aluminum rod that sacrifices its life for that of the water heater, thereby helping in extending its life.
You should replace your water heater anode after every 5 years. If you live in an area with hard water (which increases the rate of corrosion), you should replace the rod after every 3 years. Regular inspection of the anode rod is however recommended.
Foul smelling hot water (usually a sulfur/rotten eggs smell) and a reddish-brown discoloration of the water are the 2 clear signs of a bad//fully used anode rod. You may also hear a pinging sound from the heater, if the anode rod breaks off and starts rattling about.
To replace your water heater anode rod, turn off the power/gas supply, close the cold water valve and drain about 2 gallons of water from the tank. Use a 1 1/16” socket wrench to loosen the anode rod hex head. Pull it out and replace it with the new one. Open the water and turn on the power/gas.
Water heater anode rods cost $50 or even less. If you decide to replace it yourself this will be your only cost. It will however cost you between $150 to $250 to have a professional plumber replace it for you, depending on your area and scope of work.
Water heater anode rods are universal. The hex heads of these rods are all 1 1/16” which makes anode rod interchangeable, although their lengths vary. This however applies if the anode rode is installed at the top of the water heater and not at the hot water connection nipple.
How an Anode Rod Works
A water heater is made of steel. That makes it strong and will be able to hold high water temperature and pressure, preventing it from bursting.
Steel has however one main problem. It corrodes. And when it corrodes, it weakens thereby compromising its structural integrity, as well as causing water discoloration due to the rust.
To help the water heater last long, manufacturers will install a thin glass lining inside the water heater to shield it from corrosion. The glass however breaks, and when that happens corrosion is inevitable.
That is where the anode rod comes in. As a second line of defense. Water heater manufactures install a long rod of one of the least noble metals (corrodes easily), whose life is sacrificed for that of the water heater.
The corrosive elements in the water chooses to react with the anode rod, instead of the water heater lining. This is how an anode rod helps to prolong the life of the water heater.
If the anode rod is completely eaten away and you fail to replace it, the elements will then turn to the water heater itself and start attacking it. If this continues, a hole will develop and the water heater will start leaking, especially from the bottom.
Apart from replacing the anode rod, another thing you can do is to frequently drain and flush your water heater. This helps to remove sediments which sit at the bottom of the tank, corroding and eating it away. More on that in this post.
How to Replace a Water Heater Anode Rod
Replacing a water heater anode rod is not that difficult. You however need to do it safely. It is important to know that the water inside the water heater is scalding hot, and you therefore need to observe safety practices keenly.
The following are the steps to follow when replacing a water heater anode rod:
1. Shut off Water Supply.
You cannot replace the anode rod with cold water still flowing to the tank. locate your cold water supply valve and turn off the shut off valve.
If you have a gate valve, turn the knob all the way clockwise. For a ball valve, shut off valve by turning the handle such that it forms a 90 degrees angle with the water pipe.
If unfortunately you do not have a shut off valve for your water heater (highly unlikely) you will need to shut off water to your entire house, and drain water from the lowest faucet.
2. Turn off Power/Gas Supply
You don’t need the water to keep heating up while working on the water heater. It is not only unsafe, but it could also cause the heating element to burn as well.
If you have an electric water heater, turn off power at the circuit breaker. With a natural gas-powered water heater turn off gas to the pilot.
3. Drain out Some Water
Although the water supply to the water heater has already been turned off, the tank is still full of hot water. Removing the anode rod in that condition will cause the water to spill on your floor.
There is also a risk of the hot water splashing on your face, since the pressure and temperature of the water is still high. For that reason, you need to drain out some water from the tank.
Connect a garden hose to the drain valve at the bottom of the water heater, and direct its other end out into the driveway or a floor drain. Use a flathead screw driver to open the drain valve and drain out about a gallon or 2 of water.
Note: You only need to drain out just a little amount of water. The weight of the water will be very vital in holding the water heater in place as you loosen the anode rod. An empty or even half full water heater will topple easily.
4. Remove the Anode Rod
Depending on your water heater manufacturer, the anode rod hex head will either be sunken below the top of the water heater, or will have slightly protruded out. With a sunken anode rod hex head, you will surely need to have a socket wrench, while any other type of wrench will suffice for a protruding hex head.
Please note that some anode rod hex heads are concealed using a plastic cover. In this case, you will need to pry off the cap with a flathead screw driver to access the hex head.
Engage the socket wrench on the anode rod hex head and attempt to turn it counterclockwise to loosen it. If the anode rod has never been replaced or has been in place for a long time, it will surely not come off that easily.
Slip a cheater/breaker bar in the socket wrench to give yourself more leverage. As you do that it is very important that you enlist the services of a helper or even 2 of them to hold the water heater in place. You want the water heater to remain solid in place as twisting it could break water pipes, or even undo your efforts.
Note: Don’t be tempted to take a hammer and start banging the hex head in a desperate need to break it free. That will either destroy the inner lining of the water heater or even the threads.
Some people don’t recommend it but if you have tried the breaker bar but the anode rod will just not break loose, spray the hex head with a penetrating oil or even a spray like WD-40. After you have sprayed the oil wait for about 15 minutes then try again.
Once the socket wrench start turning freely, remove the socket and unscrew the rod with your hand. If you do not have enough overhead space to pull out the anode rod, try to pull bend it as you pull it.
Another option you can do is to cut it into smaller pieces as you pull it out. This piece is junk so there is no need to preserve it as it is.
To prevent dropping it back in the tank, pull it as much as you can then grab it with a vice grip. Cut the piece above the and then pull it out some more until you pull all of it out.
5. Install the New Anode Rod
Before installing the new anode rod, grab a towel and clean the opening where the old anode rode was installed. Use a toothbrush or wire brush to clean the threads, especially if there is rust or mineral deposits embedded.
Tip: If the space above your water heater is not enough to install a solid anode rod, go with a flexible one. A flexible anode rod can be easily bent, allowing it to easily go inside the water heater.
Before inserting the anode rod inside the water heater, apply about 6 wraps of Teflon tape around its threads. Since to install the anode rod you will need to turn it clockwise, you should apply the Teflon tape in a counterclockwise direction to prevent it from coming off.
Insert the anode rod and turn it clockwise until it is hand tight. Use the socket wrench to tighten it further. There is no need to use the breaker bar for this step.
6. Turn the Water Back On
With the anode rod nicely in place, it is time to turn on water supply back. If you have not flushed your tank for sometime (ideally should be done once a year), now would be a good time to do it.
Instead of turning the water back on, keep it shut and instead drain the entire water heater. If the last bit of the water is dirty or rusty, you need to flush the tank.
To do that, open the cold water shut off valve. The water will strike the bottom of the tank hard, agitating and dissolving the sediment. Let the water flow out until only clean water can flow out.
Turn off the drain valve and let the tank to start filling. To prevent air from being trapped, open your closest hot water faucet. This will allow the air to be flushed out.
Keep monitoring the open faucet, at first, water will be sputtering out as the air exits the tank but as soon as all of the air has been flushed out a constant flow will be observed. Turn off the faucet at that time.
7. Turn on the Power/Gas Back
With the tank now full of water, turn on the power to your water heater of gas supply if you have a gas-powered water heater. Wait for about 20 minutes for the water to heat up sufficiently.
Monitor the anode rod connection for leaks. Remember that as water is heated, it expands. The only way to see a leak is if the water is hot enough. In case of a leak tighten the hex head a little bit more.
Magnesium vs Aluminum Water Heater Anode Rods
Water heaters are usually installed with aluminum or magnesium anode rods. Both of these rods have their advantages and disadvantages.
When it comes to doing the actual job that thy are actually meant to do, magnesium anode rods are way more effective than aluminum rods. They react quite fast with the elements in the water, thereby preserving the life of your water heater.
Aluminum anode rods on the other hand are less expensive than magnesium ones and are also more durable.
One of the major disadvantages of magnesium rods is that they react with elements in the water producing hydrogen sulfide gas. If you have ever experienced a sulfur or rotten eggs smell in your faucets or hot water then this is the reason.
You however don’t need to worry if the magnesium is dissolved in the water as it provides health benefits to our body. The same cannot however be said of aluminum.
Cannot Remove Anode Rod from Water Heater?
There are 2 things you can do if you are unable to remove an anode rod from the water heater. Leave it and wait for the water heater to fail, or call in a professional plumber to help.
Of the 2, I prefer to leave the anode rod in place. There is no guarantee that even if you bring in the plumber he will manage to remove it. If you can’t do it, what will he do different? And the cost will just be too high.
Another option is to replace the water heater altogether. This is especially the case if the water heater is older than 10 years. Read more on when to replace a water heater in this post.