Anode Rod
A sacrificial metal rod inside a tank water heater that corrodes in place of the steel tank, protecting it from rust for as long as the rod lasts.
An anode rod is a length of magnesium, aluminum, or zinc alloy threaded into the top of a tank water heater. Through a process called galvanic corrosion, the rod attracts the chemical reactions that would otherwise eat the steel tank, sacrificing itself so the tank survives. It is the single most important reason a water heater lasts a decade rather than a few years, and it is also the part homeowners most often forget exists.
A rod has a finite life, typically 3 to 5 years, faster in soft or softened water, slower in some hard-water areas. Once it is consumed down to the steel core wire, the tank itself becomes the sacrificial metal and rust begins. By the time you see rusty hot water or hear about a leaking tank, the rod is usually long gone. Checking and replacing the rod on schedule is the most economical way to extend a water heater well past its rated life.
There is a comfort angle too. A magnesium rod reacting with sulfate-reducing bacteria is a common source of the rotten-egg smell in hot water, and switching to an aluminum-zinc rod often clears it. The trade-off is that the rod must be reachable and the tank not already rusted through. Pulling a seized rod from a fifteen-year-old tank is sometimes the moment a homeowner learns the heater is due for replacement anyway.
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- Dip Tube : A long tube inside a tank water heater that delivers incoming cold water to the bottom of the tank, so it heats before rising to the hot outlet at the top.
- Recovery Rate / First-Hour Rating : Two related capacity measures: recovery rate is how fast a heater reheats water, and first-hour rating is how much hot water it can deliver in the first hour of heavy use.
- Heat Pump Water Heater : A high-efficiency electric water heater that moves heat from the surrounding air into the tank instead of generating it directly, cutting energy use by 60 to 70 percent.