Water Heater Anode Rod: What It Does and When to Service It
By Mike Holt, NJ Master Plumber · November 1, 2026 · 3 min read · Updated November 1, 2026
Quick answer
The anode rod is a metal rod inside a tank water heater that corrodes on purpose so the steel tank doesn't. Replacing it is professional maintenance, not a homeowner job, because energy and pressure have to be isolated per the manufacturer's instructions and old rods can be stuck tight. You can watch for the signs: rusty hot water, a rotten-egg smell and the heater's age.
- Difficulty
- Call a professional
- Time
- A few minutes to look. No hands-on work
- You need
- Flashlight, a clear glass
Rather not risk it? A licensed plumber can handle this for you, with written upfront flat-rate pricing options before any work starts.
Every tank water heater has a sacrificial anode rod screwed into the top of the tank. It's an inexpensive part, and once it's used up the tank starts to rust from the inside. Replacing it is professional maintenance. Here's what you can safely look for from the floor, and what a plumber does from there.
What you can check on your own
All of this is looking and listening. Don't shut anything down, drain the tank or put a wrench on the rod.
Step 1: Find the heater's age
The rating plate on the side of the tank lists the model and serial number, and often the date. If the heater is more than about 4 or 5 years old and nobody has checked the rod, it's worth asking about at your next service.
Step 2: Compare hot and cold water
Fill one clear glass from the hot tap and one from the cold. Rusty or brown water from the hot side only can mean the inside of the tank is rusting. A rotten-egg smell from the hot water only can also point to the rod.
Step 3: Look at the top of the tank
From where you can see it safely, look for rust, crust or a drip around the fittings on top, and note how much ceiling room there is above the heater. That helps when you call. Don't loosen anything.
What replacing an anode rod involves
A plumber isolates energy and pressure per the manufacturer's instructions before opening anything. After years of heat, rods are often stuck, and forcing one on an aging tank can damage the tank or the pipe connections on top. That's why we don't recommend it as a homeowner job.
A rod is used up when the steel wire in the center is showing, or it's thin and pitted along most of its length.
Which anode rod is right?
Your plumber will match the rod to your water and your heater. These are the usual options:
| Type | Best for | Note |
|---|---|---|
| Magnesium | Most homes with normal or soft water | Protects best, wears fastest |
| Aluminum | Hard water | Lasts longer in hard water |
| Zinc-aluminum | Hot water that smells like rotten eggs | Cuts the sulfur smell from bacteria |
| Powered anode | Persistent smell, or a long-term fix | Doesn't wear away; plugs into an outlet |
Signs your anode rod is used up
- The heater is more than about 4 or 5 years old and the rod has never been checked
- Rusty or brown hot water, while the cold water is clear
- Hot water that smells like rotten eggs
- Popping or rumbling from the tank, which often comes with heavy sediment
- Flakes or grit showing up in faucet screens
Why leave it to a plumber?
Anode rods are often stuck tight after years of heat, and forcing them can twist the tank or crack the pipe connections on top. There may be no ceiling room to pull the rod, or the tank may be old enough that a new rod won't buy much time. We check the anode rod, relief valve, venting and sediment during a yearly water heater service. Written upfront flat-rate pricing options. You choose. See water heater repair and replacement.
Plumbing Doctor is a veteran-owned NJ Master Plumber in Somerset, serving Central New Jersey. Call 908-873-6686 to book a water heater check.
Get tips and reminders
New guides and seasonal reminders. A few emails a year.
Stop and call us if
- The hot water is rusty or brown while the cold water is clear.
- The hot water smells like rotten eggs.
- The heater is more than about 4 or 5 years old and the rod has never been checked.
- You see rust, crust or a drip on top of the tank.
- Someone has tried to loosen the rod and it wouldn't move.
Call 908-873-6686.
Michael Holt
Owner and operator of Plumbing Doctor, NJ Master Plumber (Lic. #36BI01345600) and U.S. Marine Corps veteran.
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