How often should you replace a water heater anode rod?
Updated July 2026
Inspect the sacrificial anode rod every 3 years and replace it once it is more than half eaten away, which usually lands somewhere between 3 and 5 years (every 2 years in softened water, which devours anodes). The rod is a length of magnesium or aluminum that corrodes on purpose so the tank's steel does not. At $30 to 60, swapping it is the single cheapest thing you can do to keep an 8 to 12 year tank from rusting through early.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| City water, standard tank | Every 3–5 years | Check at year three, replace when half consumed |
| Softened water | Every 2 years | Softener salt accelerates anode consumption sharply |
| Well water with a rotten-egg smell | Switch rod type | A powered or zinc-alloy rod cuts the sulfur odor |
| Rod is bare wire or thickly caked | Replace now | Once the steel core shows, the tank is next to corrode |
| Tank 8+ years, never checked | Inspect first | A long-neglected rod may mean corrosion is underway |
The cost of skipping it
What skipping it costs: once the anode is fully consumed, corrosion moves on to the tank walls, and a rusted-through tank cannot be repaired, only replaced. That is a $1,500 to 2,500 job, versus a $30 to 60 rod and an hour of work. A neglected anode is the top reason tanks die at year six instead of year twelve. Pair the check with an annual flush and you can push a tank well past its average life.
How to do it (30–60 minutes · Moderate DIY, or add to a plumber visit)
- Shut off power or set gas to pilot, close the cold inlet, and drain a few gallons to drop the water level below the top.
- Find the hex head on top of the tank (sometimes hidden under a plastic cap or the sheet-metal top).
- Break it loose with a 1 1/16-inch socket and a breaker bar; a helper may need to steady the tank.
- Lift the rod out and inspect: replace it if the core wire shows, it is under half its original diameter, or it is heavily caked.
- For tight ceilings, buy a flexible segmented anode that bends in; wrap the threads in PTFE tape before installing.
- Torque it snug, refill the tank with a hot tap open to purge air, then restore power or gas.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing anode rod swaps schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
What does a bad anode rod look like?
A healthy rod is a solid cylinder of magnesium or aluminum. A spent one is chewed down to the bare steel support wire in spots, reduced to under half its original diameter, or so heavily coated in calcium scale that it can no longer sacrifice itself. Any of those means replace it now. If it looks nearly new after three years you have soft water and can stretch the interval; if it is gone, the tank has been unprotected and needs closer watching.
Why does my hot water smell like rotten eggs?
That sulfur smell is usually a reaction between a magnesium anode rod and sulfate-reducing bacteria in the water, common on well systems. The fix is not removing the rod (that leaves the tank unprotected) but switching to an aluminum-zinc or a powered impressed-current anode, which does not feed the reaction. Flushing the tank and briefly raising the temperature can also knock the bacteria back. Never leave a tank running with no anode just to stop the smell.
Does a water softener affect the anode rod?
Yes, significantly. Softened water is more aggressive toward the sacrificial anode, so it corrodes roughly twice as fast, meaning a two-year check instead of three to five. That is the trade-off: softening protects the tank and appliances from scale but eats the anode quicker. If you soften your water, put the anode inspection on a tighter cycle, because a rod that vanishes in two years leaves the tank exposed for the rest of its life.