Part of our guide to Tankless vs Tank Water Heater — The Real Trade-off
Nearly every water heater question reduces to one distinction: is the tank leaking, or is a part failing? Those have completely different answers.
Water from the tank itself means replace. A corroded tank cannot be repaired. Water from a fitting, valve or connection, or a unit that heats poorly, is usually a part — and parts are comparatively cheap.
Symptoms that are usually a part
No hot water at all — often a thermostat, a heating element, or on gas units the thermocouple or pilot assembly.
Not enough hot water — commonly sediment or a failed lower element rather than an undersized tank.
Water too hot — usually a thermostat.
Noise, rumbling or popping — sediment on the tank floor. Flushing sometimes helps; it also signals the unit has been running harder than it should.
Discoloured water — frequently an exhausted anode rod, which is itself a warning that the tank is now the thing corroding.
The symptom that decides it
Water pooling under the tank, coming from the tank body.
That is corrosion through the tank wall. There is no repair. It will worsen, and a failed tank empties its full contents onto the floor.
Check carefully first: condensation, a leaking temperature-and-pressure valve, or a loose fitting can all look like a tank leak and are not.
The anode rod is a sacrificial component that corrodes in place of the tank. Once consumed, the tank starts corroding instead. Replacing it periodically is the cheapest thing available to extend a tank heater's life — and it is skipped so routinely that many owners have never heard of it.
Deciding
Repair when the unit is not near the end of its expected life, the tank is sound, and the fault is a recognised part.
Replace when the tank leaks, when the unit is old and needs a significant repair, or when repeated faults have begun. At that point you are spending on a unit that will need replacing shortly anyway.
Related reading
This is general information — see our disclaimer.
Frequently asked questions
Which failures are cheap to fix?
Thermostats, heating elements, thermocouples and valves are commonly replaceable parts rather than reasons to replace the unit.
Which failure ends the unit?
A leaking tank. Once the tank itself has corroded through it cannot be repaired, and it will get worse rather than better.
How long do they last?
Tank units typically give years of service that varies widely with water hardness and whether the anode rod was ever replaced. Age plus a tank leak is decisive.
What is an anode rod?
A sacrificial rod that corrodes so the tank does not. Replacing it periodically is the single cheapest way to extend a tank heater life, and almost nobody does it.
Sources
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