The anode rod is a sacrificial metal rod inside the tank that corrodes preferentially to protect the steel tank from rusting. State factory-installed anodes are magnesium (volume models) or aluminum (some XE and Premier Hybrid). Replacing the anode rod every 4-7 years is the single highest-ROI water heater maintenance task — it can double the tank lifespan.
Why the anode rod matters
Tank water heaters fail when the inside of the steel tank rusts through. The anode rod corrodes instead of the tank. Once the anode is consumed (depleted to a thin wire core), the tank itself starts corroding. End-of-life follows 2-4 years later.
Replacement schedule
| Water hardness | Replace |
|---|---|
| Soft (under 7 gpg) | Every 5-7 years |
| Medium (7-11 gpg) | Every 4-5 years |
| Hard (over 11 gpg) | Every 3-4 years |
| Very hard or well water | Every 2-3 years |
Magnesium vs aluminum-zinc vs powered
- Magnesium — factory standard on most State units. Best performance in standard water; can cause sulfur smell in well water
- Aluminum-zinc — replacement option that eliminates sulfur smell issues. Slightly less corrosion protection but adequate
- Powered anode — electric impressed-current option. Never needs replacement, eliminates sulfur smell. $150-250 vs $30-50 for sacrificial
DIY replacement
- Turn off the breaker (electric) or gas (gas units)
- Close cold supply valve
- Open hot tap to relieve pressure
- Locate the anode hex head on top of tank (under plastic cap; remove insulation if needed)
- Use 1-1/16" socket on a breaker bar (anode is torqued to 75-100 ft-lb)
- Unscrew counter-clockwise; pull rod up (may be flexible-segmented for low-clearance installs)
- Inspect: rod consumed to less than ½" diameter or showing exposed steel wire = replace
- Wrap new rod threads with Teflon tape
- Install and torque to 75-100 ft-lb
- Restore water supply
- Restore power/gas
Cost
- Magnesium anode rod: $30-45
- Aluminum-zinc anode rod: $40-55
- Powered anode: $150-250
- Flexible (segmented) anode for low-clearance installs: $50-70
- Pro replacement: $100-200
Sulfur smell fix
Magnesium anodes can react with sulfate bacteria in well water, producing rotten-egg-smell hydrogen sulfide. Switch to aluminum-zinc or powered anode and the smell goes away within days. See sulfur smell hub.
Bottom line
Replace every 4-7 years (sooner in hard water). Cheapest, highest-ROI tank water heater maintenance task. Aluminum-zinc if you have well water and want to prevent sulfur smell.