Typical service life by type, the four warning signs that come before failure, and why the anode is what decides most of it.
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Maintenance and lifespan
A storage tank does not die of old age. It dies because a part that costs very little was never replaced, and nobody told the owner it existed.
Three parts nobody mentions until the tank has already gone
Storage hot water systems are one of the few appliances in a house where routine maintenance genuinely doubles the life of the thing: and one of the few where almost no owner is ever told what that maintenance is.
The sacrificial anode is a rod inside the tank that is designed to corrode instead of the tank wall. When it is used up, the tank starts corroding. Replacing it is a scheduled job on most tanks, and skipping it is the single most common reason a system fails years earlier than it should. The temperature and pressure relief valve is a safety device that is supposed to be eased periodically; a valve that has never been touched can seize. And a valve that drips constantly is telling you something. The tempering valve limits the temperature delivered to bathroom outlets and, like anything with a moving part in hot water, it drifts and eventually fails.
Water chemistry matters more than brand. The same tank in a hard-water or high-chloride area will not last as long as it does elsewhere. And the anode type is supposed to be chosen accordingly. If you are on tank or bore water, see water quality, because what is in the water is also what is eating the cylinder.
Maintenance guides
Why the bathroom runs lukewarm while the kitchen scalds, the four other valves people confuse it with, and why it wears out before the tank does.
Stored temperature and delivered temperature are set by two different parts. What a failing thermostat looks like from outside the cabinet, and why turning it up is the wrong fix.
The cylinder warranty and the parts warranty are different periods, and the anode is usually the condition attached to the longer one.
The rod that corrodes so the cylinder does not, why there is no warning when it is spent, and why a pristine rod is bad news.
A failed element and a drifting thermostat look identical from outside the cabinet. What separates them, and the Australian cause that is not a fault at all.
Four different devices carry the name and they save different things. Why the distance between heater and tap decides more than any of them.
The safety valve on your tank does nothing on a normal day. What it protects against, what a drip means, and why nobody should cap it.
A blanket on a modern tank adds little and can break the rules. Why lagging the pipes is usually the better buy.
The valve that stops water flowing into your system. Where it usually sits, when to close it, and what to leave alone.
The small flame sensor that shuts the gas off. What it protects against, and why repairs are for a licensed gasfitter.
Power first, then water, and the point where you stop and call a licensed plumber or gasfitter.
The yearly checks you can do, the parts that need a licensed plumber, and what is not worth doing.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- Australian Government, energy.gov.au. Hot water systems — types, installation and energy performance
- Australian Building Codes Board. National Construction Code — Volume Three (Plumbing Code of Australia)