How Long Do Water Heaters Last?

The honest answer to how long a water heater lasts is that it depends on the water it runs on and whether anyone maintained it. The ranges below are what plumbers work to, and they are what the rest of this site uses consistently.

A conventional tank heater - gas or electric, 40 or 50 gallons, in a garage, closet or attic - generally gives eight to twelve years of service. In hard water with no flushing, failures at the lower end are common. In softened water with an annual flush and a replaced anode rod, the upper end is realistic.

A tankless unit can run considerably longer, because there is no steel tank sitting full of heated water waiting to corrode through. What it has instead is a heat exchanger that scales, so its life depends almost entirely on whether it is descaled on the schedule the manufacturer requires. A neglected tankless unit in hard water can fail early; a maintained one outlives two tank heaters.

• Tank heater: about 8 to 12 years, lower end in hard water with no flushing
• Tankless: considerably longer than a tank, but only if descaled on schedule
• Anode rod: a wear part, and replacing it extends a tank's life
• The data plate on the unit carries its manufacture date - check it before you worry

The failure mechanism in a tank heater is corrosion, and sediment accelerates it. Dissolved calcium and magnesium stay in solution in cold water and drop out when it is heated, settling on the bottom of the tank above the burner in a gas unit or caking onto the element in an electric one. That layer insulates the heat source from the water, so the burner runs longer and the steel at the bottom of the tank runs hotter than it was designed to.

You experience that in sequence: popping and rumbling as water boils in pockets under the sediment, then hot water running out sooner because sediment has displaced usable volume, then a utility bill that creeps up, then the failure. North Texas water carries enough hardness for this to be the normal path rather than the exception - the North Texas Municipal Water District, which supplies much of the region, describes its treated water as moderately hard, and the City of Mesquite publishes its own average between 93 and 134 milligrams per liter.

The glass lining inside a tank and the sacrificial anode rod are what hold corrosion off. The anode is consumed by design, and once it is gone the tank itself starts corroding. That is why a heater that has never had its anode checked at seven or eight years old is on a shorter clock than one that has.

Four things make a measurable difference, and none of them are expensive compared with a replacement.

• Flush the tank annually. It removes loose sediment before it hardens into a layer a flush cannot lift. In water this hard, once a year is a minimum.
• Have the anode rod checked. It is a consumable part, and replacing a spent one is far cheaper than replacing the tank it was protecting.
• Control water pressure. A failed pressure-reducing valve, or a closed system with no working thermal expansion tank, loads the tank and the relief valve every heating cycle. That is invisible wear.
• Soften the water, if hardness is a whole-house problem. A softener attacks the cause, and the same benefit reaches your fixtures, your dishwasher and your washing machine.
• On a tankless unit, descale on the manufacturer's schedule - it is usually a warranty condition, not a suggestion.

Age alone is not a verdict, and a healthy twelve-year-old heater does exist. But age plus any of the signs below means you are deciding between a planned replacement and an unplanned one, and the planned version is always cheaper and drier.

• Rusty or discolored hot water - a spent anode rod, or a tank corroding internally
• Popping or rumbling that a flush no longer quiets - hardened sediment
• Hot water that runs out noticeably sooner than it used to
• Moisture, rust or staining at the base of the tank - the one sign that is never a repair
• A relief valve that weeps - pressure or expansion, and worth diagnosing immediately
• Repeated repairs on a unit past ten years - each part buys less time than the last

There is a real argument for replacing a heater on your own schedule once it is past about ten years, and it has nothing to do with upselling. A planned replacement happens on a weekday at a quoted price with time to compare options, including whether a tankless unit or a softener makes sense. An emergency replacement happens with forty or fifty gallons already on your floor, from whoever can come today, at whatever that costs.

Where the unit sits should weight that decision. A heater in a garage with a floor drain is a low-consequence failure. One in an interior closet on a slab, or on an attic platform above finished ceilings, is not - and in those locations a drain pan piped to a visible termination is essential rather than optional.

Dallas Best Plumber is a free referral service, not a plumbing company. Tell us the age, type and location of your heater and what it is doing, and we match you with a licensed, insured local plumber who can service it, tell you honestly how much life is left, or quote a replacement - free and with no obligation.