USA Expert Plumbing

How to check and replace a water heater anode rod

By USA Expert Plumbing Editorial Team. Updated . 2 min read.

Short answer

The anode rod is a metal rod inside a tank water heater that corrodes on purpose so the steel tank does not. Check it every few years; replace it when much of the rod is eaten away and the steel core wire shows. A new rod typically costs a few dozen dollars, and a plumber usually charges about $100 to $350 including labor.

In this guide
  1. How often to check it
  2. Signs it is used up
  3. Types of anode rods
  4. How the replacement is done
  5. Is it worth it?

Every glass-lined steel tank water heater has at least one anode rod screwed into the top. Water slowly attacks metal, and the anode is designed to be attacked first. As long as it has metal left, the tank is protected. Once it is gone, the tank starts to corrode, and a corroded tank eventually leaks.

How often to check it

Check it every few years, and more often with softened or hard water, which can use up an anode faster. Your heater's manual may give a specific interval.

Signs it is used up

  • Much of the rod is thin, pitted or gone
  • The steel core wire is visible along a large part of its length
  • Heavy crusting of scale covering the rod

Types of anode rods

TypeGood to know
MagnesiumCommon standard rod; strong protection in most water
Aluminum or aluminum-zincOften chosen when water causes a rotten egg smell
Powered anodeUses a small electrical current instead of wearing away; costs more
Flexible (segmented)Bends to fit where there is little headroom above the tank

A rotten egg smell only from the hot water is often a reaction between bacteria in the water and the anode. Switching to an aluminum-zinc or powered anode is a common fix. Ask a plumber which fits your water.

How the replacement is done

  1. Turn off the gas or the power to the heater, and close the cold water supply.
  2. Open a hot tap to relieve pressure, then drain a few gallons from the tank's drain valve.
  3. Locate the anode's hex head on top of the tank; some share a fitting with the hot water outlet.
  4. Break it loose with a large socket and breaker bar. It is often very tight.
  5. Wrap the new rod's threads with thread sealant tape, install it and tighten it.
  6. Refill the tank with a hot tap open until water flows steadily, check for leaks, then restore gas or power.

The water inside may be hot. Let it cool before draining. If the old rod will not budge, stop before damaging the tank fitting and call a plumber.

Is it worth it?

On a tank under about eight years old, a new anode can help it reach or exceed its expected life. On an older tank that already shows rust in the water or at the fittings, the tank may already be corroding, and replacement is often the better investment. See our water heater maintenance cost guide for typical service prices.

Common questions

How long does a water heater anode rod last?

It depends heavily on water chemistry. Many last several years, but softened or aggressive water can use one up much faster. Checking it is the only way to know.

Can I run a water heater without an anode rod?

You should not. Without it, the steel tank corrodes faster and is likely to leak sooner.

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