The anode rod is the reason a steel water heater tank does not rust from the inside out within a few years of installation. It is a sacrificial magnesium or aluminum rod suspended in the tank that corrodes electrolytically in place of the tank’s steel shell. When the rod is depleted, that protection ends — and the tank begins corroding. In Triangle water at 9 to 11 grains per gallon, most residential anode rods deplete in 3 to 5 years. Drain Express inspects anode rods as part of every maintenance visit and carries common sizes for same-day replacement.
What Depletion Looks Like
A healthy anode rod is a solid magnesium or aluminum shaft roughly 3/4 inch in diameter. A depleted rod looks like a thin wire of remaining core metal — or nothing at all if the rod has been gone long enough that only the steel cable center remains. When we pull a rod that is down to the cable with no sacrificial metal left, the tank has been unprotected for some period of time, and we inspect the tank lining for early corrosion before recommending a path forward.
Rust-colored or metallic-tasting hot water is often the first sign a homeowner notices that the anode rod has been depleted for a while. The discoloration comes from corrosion of the tank shell. At that stage, a new anode rod may slow further corrosion but the tank is already compromised — replacement is likely within 2 to 3 years regardless.
Anode Rod Types in Triangle Homes
Magnesium anode rods are standard in most residential water heaters and are the more effective sacrificial material in the moderate-hardness water common across Durham and Chapel Hill. Aluminum/zinc rods are used in areas with very soft water or in homes that have noticed a sulfur smell from the water heater — the zinc inhibits the sulfur-reducing bacteria that produce the rotten-egg odor.
Some Bradford White units use a powered anode (impressed current) rather than a sacrificial rod — these require periodic inspection to verify the power supply is functioning rather than rod replacement.
Combination Rod and Dip Tube
Most current residential water heaters have a combination unit at the cold water inlet port — the dip tube (which directs cold water to the bottom of the tank) and the anode rod are integrated in a single assembly. Replacing the anode on these units also replaces the dip tube, which can develop cracks over time and cause cold water to short-circuit to the hot outlet.
How Often to Replace
Annual inspection starting at year 3 in Triangle water. Replace when the rod is depleted to less than 1/2 inch diameter or when the core cable is exposed. In homes with a water softener, depleted anode rods can appear sooner than the 3-year mark because softened water is more aggressive toward sacrificial metals.
Related Services
- Water Heater Sediment Flush
- Annual Maintenance Overview
- Tank Water Heater Repair
- Water Heater Replacement