How do I find out how old my water heater is?

The serial number on the rating plate encodes the build date, and every manufacturer uses a different scheme. The most common pattern puts the month and year in the first four characters — a serial beginning 0619 usually means June 2019. Rheem, A.O. Smith, Bradford White and State each publish a decoder on their support site; Bradford White uses a letter for the year and a second letter for the month, which catches people out. If the plate is unreadable, an installation sticker on the side or the permit record at your building department will often date it.

Does a longer warranty mean a better water heater?

Usually, yes — but indirectly. Manufacturers sell 6, 9 and 12-year versions of what looks like the same tank, and the difference is typically a larger or second anode rod, a thicker glass lining and sometimes heavier elements. The longer-warranty model costs $100 to $250 more and is generally the better buy, because the extra anode metal is precisely what delays tank corrosion. Note that the warranty covers the tank, not labor, and it is void in many cases if the unit was installed without a required permit.

Is it worth replacing the anode rod?

On a tank under about eight years old with no leaks, often yes. The rod is a sacrificial magnesium or aluminum bar that corrodes so the steel tank does not, and it is the single component most responsible for tank life. A replacement rod costs $25 to $60 and inspection is a 30-minute job, though the hex plug on an older tank is frequently seized and needs a breaker bar. On a tank past ten years the economics are marginal — put the money toward the replacement.

Can a water heater last 20 years?

Tank units occasionally do, almost always in soft-water homes where the anode rod was replaced at least once and the tank was flushed annually. It is the exception, not a target. Tankless units reaching 20 years is normal rather than remarkable, because the heat exchanger can be descaled and most failing parts — igniters, flow sensors, control boards — are replaceable. Past year 12, the sensible question for a tank is not whether it will last but what it will cost when it goes.

What happens when a water heater fails?

Two ways. The slow way is falling capacity and rusty water as the lining fails, which gives you weeks of warning. The fast way is a seam or fitting letting go and dumping the full tank — 40 to 80 gallons — onto the floor, then continuing to run until someone shuts the cold inlet. A drain pan plumbed to a drain, plus a leak alarm at $15 or an automatic shutoff valve at $150 to $500, is cheap insurance on any tank past year eight, especially one in a finished space.

How Long Does a Water Heater Last? Tank vs Tankless Lifespan

Written & researched by Priya Anand DIY & Tools Editor

Updated October 2026

Low-angle view of a person's hands tightening a fitting under a kitchen sink with a wrench, in warm evening lamplight

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A conventional tank water heater lasts 8 to 12 years; the typical unit is replaced at around 10 to 11 years. Tankless units run 15 to 20 years or more, because the heat exchanger can be descaled and most failing parts are replaceable. Water quality is the biggest single variable: hard water and high temperature settings cut tank life by years, while an anode rod replaced once mid-life can add several. The US Department of Energy uses a 13-year expected life for tank heaters in its own cost models.

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How long does each type last?

The gap between types is real and mostly comes down to whether the failure point can be serviced. A steel tank fails when its glass lining and anode protection are exhausted and the shell rusts through — that is terminal. A tankless heat exchanger fouls with scale, which is reversible with a descaling flush. Gas tanks tend to fail slightly sooner than electric ones because the flue running up the center of the tank creates a hotter, more corrosive interior environment.

Type	Typical life	Usual failure mode	Common warranty
Gas tank	8–12 years	Tank corrosion, leak at seam	6–12 years
Electric tank	10–15 years	Tank corrosion; elements fail sooner but are replaceable	6–12 years
Tankless (gas or electric)	15–20+ years	Scaled heat exchanger, control board	10–15 years exchanger
Heat pump (hybrid) tank	10–15 years	Compressor or tank	6–10 years

Three-quarter view of a person's hands tightening a fitting under a kitchen sink with a wrench, in soft overcast light

What shortens a water heater's life?

Hard water is first by a wide margin. Dissolved calcium and magnesium drop out as scale on the tank floor or the heat exchanger, insulating the burner from the water, driving up shell temperature and accelerating corrosion. The US Geological Survey classes water above 10.5 grains per gallon as very hard, and much of the Southwest, Texas and the upper Midwest sits there. Second is a thermostat set high — every step above 120°F speeds corrosion and scale deposition. Third is a missing or exhausted anode rod. Fourth is high static water pressure, which stresses the tank and its fittings; anything above 80 psi should be regulated.

What are the signs a water heater is failing?

Tanks give warning if you know what to look for. Watch for these, in roughly the order they appear:

Rumbling or popping during heating — water flashing to steam under a sediment layer on the tank floor.
Less hot water than it used to make, with no change in household use, as sediment displaces capacity.
Rusty or metallic-tasting hot water only on the hot side, which points at the lining rather than the supply.
Moisture, rust streaks or mineral crust around the base or at the fittings.
Water on the floor. A tank that is actively leaking is finished; there is no repair for a rusted shell.

If you see standing water, shut the cold inlet valve on top of the tank and kill the power at the breaker or set a gas unit to Pilot or Off, then call a licensed plumber.

Wide environmental view of a person's hands tightening a fitting under a kitchen sink with a wrench, in warm late-afternoon light

How do you make a water heater last longer?

Four things, in order of payoff. Flush the tank annually — twice a year in hard water — to remove sediment before it insulates the burner; see how often to flush a water heater. Inspect the anode rod at year three and every two years after, replacing it when more than about six inches of the steel core wire is exposed. Set the thermostat to 120°F, which the Department of Energy recommends for both scald safety and efficiency — the trade-offs are in what temperature a water heater should be set to. Check static pressure with a $12 hose-bib gauge and fit a pressure-reducing valve if it reads over 80 psi.

One caveat that catches people: on a closed system with a check valve or backflow preventer at the meter, heating water has nowhere to expand, and pressure spikes on every cycle. Most jurisdictions require a thermal expansion tank in that situation. Requirements are set locally, so confirm with your building department — and note that replacing a water heater usually requires a permit, covered in do you need a permit to replace a water heater.

Should you repair or replace?

The rough rule that holds up: repair a tank under eight years old if the fault is an element, a thermostat, a gas valve or a thermocouple, since those parts run $20 to $250 and the tank has years left. Replace anything that is leaking from the tank body at any age. Past ten years, weigh a repair over about $400 against a $1,200 to $2,500 installed replacement, since you would be spending real money on a unit that owes you nothing. Related reading: why hot water runs out so fast, which is frequently a sediment or dip-tube problem rather than a dying tank.

How Long Does a Water Heater Last?