The anode rod in your water heater
The anode rod protects the steel tank in your water heater.
Updated · 3 min read
In a nutshell
The anode rod is a metal rod inside a tank water heater that corrodes so the tank does not. Once it is eaten down to the core wire, the tank starts rusting. Checking it every few years and swapping it when spent can extend the heater's life.
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What the rod does
A tank water heater is steel lined with glass. Small gaps in the lining would rust, so makers add a magnesium or aluminum rod that corrodes first and protects the steel.
That trade works only while there is metal left on the rod. When it is gone, the tank itself becomes the sacrificial metal.
Rosemead water and anode wear
San Gabriel County Water District, which serves part of Rosemead, reports hardness of 17 to 200 ppm, averaging 97.4, in its 2025 water quality report. Other suppliers serve other blocks, so check your bill.
Moderately hard water leaves scale that can coat the rod and the tank bottom. A scale-crusted rod can stop protecting even if metal remains.
Signs your rod is spent
- The heater is several years old and the rod has never been looked at
- Rusty water from the hot side only
- Rotten-egg smell from hot water
- Popping sounds along with flaky debris at the drain valve
How the check and swap go
The water and gas or power are shut off, some water is drained, and the rod is unscrewed from the top of the tank. If more than about six inches of core wire shows, the rod is replaced, per guidance from the University of Georgia extension.
Garage heaters with low ceilings may need a segmented, flexible rod. Afterward the tank is refilled, purged of air, and relit.
Rosemead owners ask
How often should the anode rod be checked?
Extension guidance suggests every few years. In harder water, earlier checks are reasonable.
Can a leaking tank be saved with a new anode?
No. Once the tank leaks, the steel is through. A new rod only helps tanks that are still sound.
Is the rod the same on a tankless heater?
Most tankless units have no anode rod. They need descaling instead.