The anode rod is a sacrificial metal component inside a gas water heater's tank, designed to corrode instead of the tank so the steel shell lasts much longer.
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Quick answer
An anode rod is a rod of reactive metal, usually magnesium or aluminum, suspended inside a gas water heater's tank specifically to corrode in place of the tank's steel shell, a process called cathodic protection. It fails by simply wearing away over years of normal operation, and once it is substantially consumed, the tank itself becomes exposed to corrosion, which is one of the main reasons tanks eventually leak and reach the end of their service life. Periodic inspection and replacement of the anode rod is one of the most effective ways to extend a tank's lifespan.
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Steel tanks would corrode relatively quickly if exposed directly to water and its dissolved minerals and oxygen over years of constant contact, so manufacturers install a rod of a more reactive metal that corrodes preferentially, a well-established principle called sacrificial or cathodic protection. As long as the anode rod has enough reactive material remaining, it continues to corrode in place of the tank's glass-lined steel interior, meaning the rod is meant to wear away over the water heater's life; a completely depleted rod is not a design flaw, it is the rod having done its job for as long as it could.
| Sign | What it suggests | Recommended action |
|---|---|---|
| Rotten-egg or sulphur smell in hot water only | Anode rod reacting with bacteria in the water | Inspect and likely replace the rod |
| Tank is 4 to 6 years old and rod has never been checked | Rod may be significantly depleted | Have the rod inspected |
| Rod inspection shows exposed steel core wire | Rod is substantially consumed | Replace the rod promptly |
| Tank already showing rust in discharged water | Possible tank corrosion already underway | Full tank assessment, not just the rod |
A sulphur or rotten-egg odour noticeable only in hot water, and not in cold water from the same home, is a fairly well-documented interaction between certain anode rod materials and naturally occurring sulphate-reducing bacteria in some water supplies, particularly on well water sources found in parts of the Fraser Valley. Switching to a different anode rod material, commonly aluminum-zinc in place of magnesium, is a common approach a technician can advise on when this specific smell pattern is present, since it addresses the chemical reaction directly rather than masking the odour.
Metro Vancouver's municipal water is comparatively soft and low in dissolved minerals, drawn primarily from mountain reservoirs, and softer water is generally a more conductive electrolyte for the anode's protective reaction, which can mean the rod is consumed at a somewhat different rate than it would be in a harder-water region. This does not eliminate the need for periodic inspection, but it is a genuine regional factor worth mentioning when a technician is setting an inspection interval, alongside the fact that homes on Fraser Valley well water may see different wear patterns given generally different water chemistry.
Noticing a sulphur smell specifically in hot water and not cold water is a useful, safe observation to report, since it is a fairly distinctive symptom pattern. Knowing roughly how old your water heater is, and whether the anode rod has ever been inspected, helps a technician judge urgency. Actually removing and inspecting the rod requires draining down the tank and accessing a fitting at the top, typically under some torque, and is best left to a technician rather than attempted as a first do-it-yourself project, particularly on an older tank where the fitting may be seized.
Safety note
Anode rod inspection and replacement is a plumbing task on the tank itself rather than a direct gas safety matter, but the water heater's gas supply and pilot should be shut off correctly by whoever performs the service, following the manufacturer's procedure. If you smell gas at any point, leave the home and call FortisBC at 1-800-663-9911.
It varies by water chemistry and usage, which is why periodic inspection rather than a fixed replacement date is the more reliable approach, especially once a tank passes several years of service.
Yes, keeping an active anode rod in place is one of the most effective ways to slow tank corrosion and extend the overall service life of a storage water heater.
That pattern is a well-documented reaction between certain anode rod materials and bacteria present in some water supplies, and a technician can often resolve it by changing the rod material.
It requires draining the tank and removing a fitting that is often torqued tightly, and it is a task most homeowners are better off having a licensed technician handle.
It is not urgent in the sense of an immediate hazard, but it should be addressed soon, since the tank itself becomes exposed to corrosion once the rod is depleted.
The region's comparatively soft municipal water is a factor in wear rate, and it is worth mentioning to your technician so they can suggest a reasonable inspection interval for your specific situation.
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