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The anode rod is the most overlooked part in your water heater, and Rheem says running without one “will greatly shorten the life of the glass lined tank.” It is a sacrificial metal rod that corrodes instead of your steel tank. Once it is used up, the tank itself starts rusting from the inside, and that is when you get a leak you cannot fix. Rheem says that as long as the rod stays in the tank in an active state, the small areas of bare steel inside the tank do not corrode.
What an Anode Rod Actually Does
Your tank is steel with a thin glass (porcelain) lining. That lining always has tiny gaps. The anode rod — magnesium or aluminum — is more reactive than steel, so the water attacks it first. Plumbers call it the “sacrificial” rod for a reason: it is designed to be destroyed so the tank is not. When the rod is gone, corrosion moves to the tank.
When to Replace It
Pull and inspect the rod once a year. Rheem says to remove it annually for inspection, and A. O. Smith says to inspect it after the first six months and at least annually after that. One Bradford White electric manual says every 2 years. On softened water, check more often: A. O. Smith, Rheem and Bradford White all say a softener wears the rod faster. Replace it when you see any of the following:
| What you see when you pull the rod | What it means | Action |
|---|---|---|
| Bare steel core wire showing for 6+ inches | Past Rheem’s replacement point | Replace now |
| Rod reduced to a thin wire / mostly gone | Tank is now corroding | Replace immediately |
| Thick crusty calcium coating | Hard-water scale; Bradford White lists calcium and lime among conditions that affect a rod | Replace if worn; have the water tested |
| Rotten-egg / sulfur smell in hot water | Magnesium reacting with bacteria | Flush and disinfect the tank; a different rod may help |
| Rod still thick, lightly pitted | Plenty of life left | Re-install, check again next year |
If your hot water smells like rotten eggs, the rod can be part of the cause, but the makers say the bacteria are the real problem — see why your water smells like rotten eggs. A powered anode is another route; Corro-Protec says its rod gets rid of the smell within 24 hours.
Magnesium vs. Aluminum vs. Powered
Magnesium is the standard rod: Rheem calls it that, and Bradford White says it best protects the steel tank. It gives up electrons more freely than aluminum, so it is used up faster in conductive water such as softened water, and Bradford White and Rheem both say it can feed the sulfur-smell reaction. Aluminum is less reactive; Bradford White says it is the better choice where softened water or low pH makes the water more conductive. For odor, A. O. Smith names a special zinc rod. A powered (impressed-current) anode is a different design: Corro-Protec says its titanium rod never degrades and highly recommends a powered anode with a water softener. The maker quotes and sources are in our guide to magnesium, aluminum or zinc anode metal.
How to Replace It (Step by Step)
This is a real DIY job, but two things stop most people: the factory torque on the rod, and low overhead clearance. Plan for both.
- Turn off power/gas and the cold-water supply. Let the tank cool. Drain a few gallons from the bottom valve to drop the level below the top port.
- Find the rod. It is the hex head on top (sometimes under a plastic cap; some rods are combined with the hot-water outlet nipple). Our anode rod size and type guide shows how to tell which you have and what fits.
- Break it loose. Use a 1-1/16″ socket on a breaker bar. Factory rods are torqued hard — a long breaker bar (or an impact wrench) is the difference between success and a stripped knuckle. Brace the tank so it does not spin.
- Pull it out. If you lack ceiling clearance, use a flexible/segmented anode rod that bends as it comes out and goes back in. Our flexible vs rigid anode rod guide compares the two.
- Install the new rod. Wrap the threads with PTFE thread tape, hand-thread to avoid cross-threading, then snug it down firmly.
- Refill and check. Open the cold supply, open a hot tap to bleed air (critical on electric heaters — never re-power an empty tank or you will burn out the elements), then restore power/gas and check for leaks at the rod.
If you would rather replace the whole unit, here is how to replace a water heater and the cost to replace a water heater.
What to Buy
Standard replacement — flexible magnesium rod. Its listing calls it a 44-inch segmented magnesium rod, which bends for tight clearance. Match your tank’s thread and old rod length first.
Powered anode rod (Corro-Protec). A different design from a sacrificial rod: Corro-Protec says it does not wear away, and its guide recommends a powered anode with a water softener. It needs a nearby outlet.
While you have the heater open, it is worth doing a full water heater flush; a sediment-heavy tank also runs noisy — see why a water heater makes noise. For new tanks, our best water heater picks compares warranties and anode setups.
Frequently Asked Questions
How often should I replace my water heater anode rod?
Inspect it once a year. Rheem says annually, A. O. Smith says after six months and at least annually, and a Bradford White electric manual says every 2 years. Rheem says to replace it when more than 6 inches of core wire shows at either end. On softened water, check more often, because the makers say a softener wears the rod faster.
Will replacing the anode rod stop the rotten-egg smell?
It may reduce it, but it does not fix the cause. Rheem says sulfate-reducing bacteria use hydrogen from the anode reaction to make the smell. A. O. Smith calls chlorination the only sure treatment, and Rheem says a new rod after a bleach flush may not be 100% effective.
Can I replace an anode rod myself?
Yes. The two hurdles are the factory torque (use a 1-1/16″ socket and a breaker bar) and overhead clearance (use a flexible/segmented rod). Always refill the tank and bleed air before restoring power.
Magnesium or aluminum anode rod — which is better?
Neither wins everywhere. Rheem calls magnesium the standard rod, and Bradford White says it protects the tank best. Bradford White says aluminum is the better choice where softened water or low pH makes the water more conductive. A powered anode is a third design; Corro-Protec recommends it with a softener.
Is it too late if my tank is already rusty?
If you only see surface staining at the rod, a new rod still helps. If the tank is actively leaking from the body, the steel has failed and no anode will save it — that tank needs replacement.
Bottom line: a yearly look at the rod, and a new one when it is worn, is simple insurance for the tank. Pull the rod, look at it, and replace it before the tank pays the price.
Related: the same galvanic reaction that consumes an anode rod attacks the tank connections — see dielectric union vs brass nipple.