Short answer
Turn off the gas or power, shut the cold supply, open a hot tap and drain a few gallons so the water sits below the top. Remove the anode with a 1-1/16 inch socket and a breaker bar while someone steadies the tank. Replace it if the core wire shows or it is heavily worn or coated. Wrap the threads of the replacement, tighten it, refill with a hot tap open until water flows steadily, then restore heat.
What you need
Steps
Find the anode
Look on top of the tank for a hex head plug, sometimes under a plastic cap or a little insulation. On some tanks the anode is built into the hot outlet nipple (a combo anode), which changes the job. Your manual shows which you have.
Turn off the heat and water
Set the gas control to pilot or off, or switch off the breaker. Close the cold supply valve.
Relieve pressure and drain a little
Open a hot tap, then drain a few gallons from the drain valve so the water is below the top of the tank.
Break the rod loose
Fit the socket and breaker bar and turn counterclockwise. Have a helper steady the tank so it does not twist the pipe connections.
Pull and inspect
Lift the rod out. If the steel core wire shows for several inches, or the rod is much thinner or caked in scale, replace it. If it is mostly intact, refit it and check again later.
Fit the replacement
Wrap the threads with sealing tape or use pipe sealant, lower the rod in (bend a flexible rod as needed), and tighten firmly.
Refill and restart
Close the drain, open the cold supply with a hot tap open until water flows steadily, check the fitting for leaks, then restore gas or power.
Which rod to put back
- Same as the old one if the water is fine: usually magnesium.
- Aluminum zinc if the hot water smells like rotten eggs: the smell guide.
- Flexible if headroom is tight. Powered if you never want to check again and have an outlet nearby.
Compare them in the anode rod guide. Rheem suggests checking the rod annually (Rheem); while the tank is partly drained, a full flush takes little extra time.
Questions people ask
How long does it take to replace an anode rod?
About an hour, most of it waiting for water to drain and refill. Breaking a stuck rod loose can add time.
What if the anode rod will not come out?
Use a breaker bar on a six point socket and have someone hold the tank so it does not twist the pipes. An impact wrench also works. Do not use heat on a gas tank. If it still will not move, a plumber has the tools.
What if there is not enough room above the tank?
Use a flexible (segmented) anode rod, which bends to go in under a low ceiling. To get the old solid rod out, you may have to bend it as you pull, or cut it.
Do I need to drain the whole tank?
No. Drain just a few gallons so the water level is below the anode fitting. It is a good moment to flush the tank completely, though.
Sources
Last reviewed October 29, 2026. Models, codes and listings change; check your heater’s manual and your local code, and follow the maker’s instructions.