Water Heater Anode Rod: When to Check It and Replace It

By Ray Bennett · Updated 2 October 2026 · 6 min read · Checked against the sources at the end

Water Heater Anode Rod: When to Check It and Replace It

Short answer

The anode rod is a metal rod inside the tank that rusts on purpose so the tank does not. When it is used up, the steel starts going instead, and a tank that rusts through is finished. Whirlpool says to check it within three years and every year after that, and replacing it for 20 to 60 dollars can add years to the tank.

Almost nobody knows their water heater has one of these, and it is the part that decides how long the whole tank lasts.

The anode rod is a long metal rod screwed into the top of the tank and hanging down inside the water. It corrodes on purpose, so the steel tank around it does not. When it is eaten away to nothing, the tank starts rusting from the inside, and a tank that rusts through is finished.

Before you start

What to carry: a torch, a 1 1/16 inch socket on a long breaker bar, thread sealing tape, a hose and a bucket. An hour.

Gas or electric, it is the same rod. Every glass lined tank water heater has one, gas or electric. A tankless heater does not.

Check the headroom above the tank. A solid rod is as long as the tank is tall. If the ceiling is too low to pull it straight out, a flexible jointed rod is the answer, and it is worth knowing before you start.

Four things to do before the socket goes on. Power or gas off first. Breaker off for an electric heater, gas control to Off or Pilot for a gas one. A heater firing with water leaving it is how elements burn out.

Cold supply off, then open a hot tap somewhere in the house. The tank is under mains pressure until you do, and a rod unscrewed under pressure lets it all out at once.

The water inside is hot enough to scald. Let it cool, or drain a few gallons through the valve at the bottom first so the level drops below the rod’s fitting: the safe order to shut a water heater down.

Hold the tank, not just the wrench. An old rod can be very tight. Brace the tank so you do not twist the pipework or tip it.

What it actually does

The rod gives up its metal so the steel tank keeps its own. Water heater makers fit one precisely because the glass lining always has tiny gaps.

Check 1

Understand why this one part sets the tank's life

The glass lining is not perfect. Every tank has tiny gaps in it, and bare steel in hot water rusts.

The anode rod protects those gaps. It is a more reactive metal than steel, so the corrosion attacks the rod first and leaves the tank alone.

It gets used up. Slowly on most water, much faster where there is a water softener, which is the one thing people rarely connect with a short tank life.

When it is gone, the clock starts on the tank. That is why two identical heaters can last very different lengths of time. One had its rod looked after.

Checking it

New, halfway, and finished. Rheem says it is time once more than 6 inches of the steel core wire shows, and Whirlpool once most of the rod is thinner than 3/8 of an inch.

Check 2Free, an hour

Pull it and judge it by eye

When. Whirlpool says within three years at the latest, then every year, and every year from the start with a softener. Rheem and GE say every year.

Find it. A large hex head on top of the tank, sometimes under a plastic cap or a little insulation. On some heaters the rod is built into the hot water outlet instead, which makes it harder to reach.

Loosen it. The 1 1/16 inch socket fits most. They are tight, so a long bar and a steady pull, anticlockwise, with the tank braced.

Read it. Thick and knobbly all the way down is fine, put it back. Rheem says to replace it once more than 6 inches of the steel core wire shows at either end. Whirlpool says once most of it is under 3/8 of an inch thick, or about a third of its length shows the wire.

Refit with tape on the threads, tighten firmly, refill the tank with a hot tap open until it runs without spitting, and only then restore gas or power.

Which rod to buy

Check 3

Pick the metal for your water

Magnesium. The strongest protection and the usual one fitted. On some water it reacts with bacteria and makes the hot water smell of rotten eggs: why the hot tap smells and the cold does not.

Aluminium and zinc. The usual cure for that smell, with slightly less protection. Fine for most houses.

Powered anode. A titanium rod fed a tiny current from a plug. It is not used up at all and it stops the smell. It costs more and needs the socket to stay powered.

Flexible or jointed rods bend in the middle so they can go in under a low ceiling. Same metal, same job.

Never just take it out and leave it out. It is a trick passed around for the smell, and it removes the tank’s only protection.

When it is not worth it any more

Check 4

Judge the tank as well as the rod

Under eight years old, a new rod is one of the best value jobs in the house.

Over ten or twelve years with the rod never changed, the tank has probably been rusting for a while. A new rod will not undo that, and the money may be better kept towards a new heater.

Rusty water from the hot tap only, or a weep at the base of the tank, means the tank itself is going: how to tell where the water is coming from.

If the rod will not move at all, a plumber with an impact gun does it in minutes. It is not worth cracking the fitting over.

Questions people ask

How long does an anode rod last?

It depends on the water. Whirlpool says softened water, hotter settings and heavy hot water use all wear it faster. That is why Whirlpool says to check it within three years and every year after that, rather than waiting for trouble.

Will replacing it stop the rotten egg smell?

Swapping a magnesium rod for an aluminium and zinc one, or a powered anode, can help, especially after the tank has been flushed and disinfected. Whirlpool says a special rod may reduce the smell but not eliminate it.

Do tankless water heaters have one?

No. They have no storage tank to protect, so their upkeep is about scale instead: what goes wrong with a tankless heater.

There is sediment when I pull the rod.

Common, and it is a good moment to flush the tank while it is drained down: how to flush a water heater properly.

Is it a job I can do myself?

If you can get the rod out, yes. The hard part is the first turn on an old rod, and the headroom above the tank. Everything else is a wrench and some tape.

Can I fit a longer or shorter one?

Fit one close to the length of the old one, measured to the tank. Too short protects less of the tank, and too long will not fit.

Sources: Whirlpool Energy Smart use and care guide 318686-001 (anode inspection, depletion signs, odor, softened water), Rheem use and care manual AP23698 (anode inspection and replacement, odor), GE GeoSpring owner's manual 49-50300-2 (annual inspection, aluminum zinc rods), Bradford White service manual 238-51542-00 (outlet anode), A.O. Smith hybrid water heater service handbook 321547-000 (anode socket size, powered anode)