OnOtto
Menu

How do you replace a water heater's anode rod?

Updated August 2026

45–60 minutes · Moderate DIY

← All how-to guides

The old rod comes out of a fitting on top of the tank and the new one threads into the same hole, which is 45 to 60 minutes of work and a $20 to $60 part. Everything hard about this job sits in one step: breaking loose a hex head that the factory torqued down and corrosion has been welding shut ever since. Check the rod every 2 to 3 years and replace it once more than half the steel core shows. That habit is what pushes a tank past the 8 to 12 year average, because the anode rod corrodes on purpose so the tank steel does not.

What you need

Before you start: The water in the tank sits at 120–140°F, so let it cool for two hours or run a long hot shower first, and crack the anode port slowly in case pressure remains behind it. Keep the breaker off or the gas control on pilot until the tank is completely refilled: an electric element that fires in a partly drained tank is destroyed in seconds. Watch your footing and your knuckles when you lean on a breaker bar at shoulder height, and never put a torch on the fitting with a gas heater in the room.

Steps

  1. Measure the headroom above the tank first. A full-length rod is about 44 inches, so with less clearance than that you need a segmented rod ($30 to $60) that bends in sections.
  2. Open the breaker on an electric heater, or turn a gas control knob to pilot. Then close the cold inlet valve at the top of the tank.
  3. Open a hot tap upstairs and drain 2 to 3 gallons through the drain valve, enough to drop the water level below the anode port. The full procedure is on how to drain a water heater.
  4. Find the hex head on the top of the tank. It hides under a plastic cap or a foam plug in the sheet metal, and on some models the anode is combined with the hot outlet nipple instead of having its own port.
  5. Break the head loose with the 1-1/16 inch socket while a helper braces the tank, so you do not twist the plumbing off the top. An impact wrench does in five seconds what a breaker bar fights for ten minutes.
  6. Pull the rod out and read it. Replace it when the steel core wire shows along more than half its length, when the metal is under about 1/2 inch thick (a new rod is 3/4 inch), or when it is armored in calcium.
  7. Wrap 3 to 4 turns of thread tape on the new rod, start it by hand so it cannot cross-thread, and snug it firmly with the socket. Overtorquing distorts the fitting and creates the leak you were avoiding.
  8. Reopen the cold inlet, let the tank refill, and purge air at the hot tap until the stream runs steady. Restore power or gas, then check the port for weeping after 10 minutes and again the next day.

Or hire it out

A plumber charges $150 to $300 to inspect and replace an anode rod, usually bundled into an annual flush. That is real money against a $20 to $60 part, but still a fraction of the $1,500 to $3,500 a replacement tank costs in 2026.

Done. Now the part everyone skips: doing it again on schedule. Log it in OnOtto and the next reminder for anode rod checks sets itself.

Log this task, get the next reminder

Frequently asked questions

Magnesium, aluminum, or a powered anode?

Magnesium gives the strongest protection and the best-tasting water, but it dissolves fastest and can last only 2 to 4 years in softened water. Aluminum-zinc costs about the same, lasts longer in aggressive water, and is the usual answer to sulfur odor. A powered titanium anode runs $150 to $250, never dissolves, and is the practical pick for a softened-water house where you are otherwise buying a rod every few years. Expected service life by type is on how long an anode rod lasts.

My hot water smells like rotten eggs. Is the anode the cause?

Almost certainly. Sulfate-reducing bacteria in the tank feed on hydrogen released by a magnesium rod and produce hydrogen sulfide, which is the egg smell. Swapping to an aluminum-zinc or powered anode removes the fuel source. Do it in the same visit as a shock treatment, since killing the existing bacteria and changing the rod together works far better than either alone. Cold water that smells the same way points at the well or the supply, not the heater.

The rod will not budge. What are my options?

In order: a 3-foot cheater pipe on the breaker bar, then a 1/2 inch impact wrench, which succeeds where leverage fails because the hammering shocks the threads loose. If it still holds, stop before you twist the tank on its connections and hand the job to a plumber. On a tank already past 10 years with no rod service, put the money toward replacement instead: see the cost of skipping anode rod replacement.

Related