Water heater anode rods come in several types, a solid rod that extends from a plug, a solid rod that extends from the outlet nipple, and a segmented or, linked rod for when there is a lack of overhead clearance. The segmented rod is available with either the plug or, outlet nipple type. You will need to determine whether your water heater takes a plug or, outlet nipple type anode. You will also need to determine if you have enough overhead clearance to get the rod in and out of the top of the water heater. The old one will bend easily but, the new one will not and needs to go in straight. If there is not enough overhead clearance you need to use a segmented anode.

This is also a good time to test the T&P Valve by lifting the handle and making sure that it discharges. Release the handle allowing it to snap closed. If the T&P valve does not open with the lever, or fails to close and leaks after testing it must be replaced. This is a critical safety device that can prevent the water heater from exploding.

You will also need to determine what kind of metal the anode needs to be made of. The most commonly available anode is magnesium, in fact that is the stock anode that comes in water heaters. Some water conditions may cause sulfur odor in the water when a magnesium anode is used. If this is the case an aluminum anode or, aluminum/zinc/tin anode rod should be used and the water heater disinfected as the odor is actually caused by a sulfur reducing bacteria.

While changing the anode does not require a complete drain down of the water heater and can be done by just lowering the water level in the tank slightly below the top I will describe how to do the work in conjunction with flushing the water heater.

1. Turn off the Water Heater. On an electric water heater, turn the water heater circuit breaker off. On a gas water heater, turn the gas valve to the off position.
2. Connect a hose to the drain valve on the heater and run to a drain or, outside. It must be lower than the water heater or, a transfer pump will be needed. Turn on the drain and allow the pressure to establish a flow.
3. Shut the cold water off to the water heater.
4. Open a hot water faucet to allow air to enter or, the tank will not drain.
5. Allow the tank to completely drain.
6. Close the hot faucet.
7. Turn back on the cold water into the water heater.
8. Allow the water to run through the water heater and out of the drain valve.  Do this for approximately five (5) or ten (10) minutes until there is no longer and debris coming out of the hose.
9. Shut off the cold water and close the drain valve.
10. Reopen the hot faucet and the cold supply valve to the water heater partially refill the water heater about ¾ full to get some weight in it.
11. Close the cold supply valve to the water heater.

You are now ready to replace the anode rod.

If your water heater has the anode on the outlet, the pipe will need a way it can be broken apart to unscrew the outlet nipple. You will also need a means of reconnecting the pipe when finished. There are many possibilities ranging from installing a union, using a repair coupling, or, a Sharkbite coupling. If you have any questions on what to do I would suggest asking at an online plumbing forum such as Terry Love’s Plumbing Forums. Unscrew the outlet nipple using a pipe wrench, and remove the old anode. You will need someone to help keeping the water heater from spinning while taking out the outlet nipple. Once it is completely loosened pull the old anode rod out. Take the new anode and apply Teflon tape to the threads of the nipple then apply Teflon paste on top of the threads. Lower the new anode into the water heater tank and thread the nipple into the water heater. Remember to have someone help you when tightening or, loosening the nipple to prevent the water heater from spinning and causing damage to the pipes.

If the anode is the plug type I use a cordless 1/2″ drive impact wrench and socket. This works very well and is the same type of equipment the factory uses for installing them. With the impact wrench there is no danger of spinning occurring. If you do not have an impact wrench, a breaker bar and socket can be used to unscrew the anode plug. However, help will be needed to prevent the water heater from spinning and pipe damage.  Once the plug is loose lift the old anode rod out of the water heater. Ready the new anode for installation by wrapping the threads with Teflon tape and apply Teflon paste over the threads. Lower the anode rod into the tank, and tighten the plug using the opposite manner from the way it was removed. Again if a breaker bar and socket is used get a helper to prevent the tank from spinning.

1. Reopen the cold water valve to the water heater and allow the tank to refill, keeping the hot water faucet open.
2. When water comes out of the faucet, the tank is full. Close the faucet. (Note: Sometimes when work of this nature is performed the aerator on the faucet may clog with debris. If the flow lowers or stops unscrew the aerator clean the debris and reinstall.)
3. Check your work for leaks.
4. Turn the water heater back on.
5. Once hot recheck for leaks.

While no water heater will last forever regular flushing and making sure the anode is protecting the water heater you should in most cases extend the life of your water heater.