How long do water heaters last?

Typical lifespan by type

Electric tanks tend to outlast gas tanks because there is no flame heating the bottom of the tank and no flue running up through the middle. Their failures are usually elements and thermostats, which are cheap to replace, while the tank itself carries on.

These are averages, not promises. A tank installed with an expansion tank, flushed every year and fitted with a new anode at year five can pass fifteen years. A tank on hard well water with high pressure and no maintenance can fail in six.

How to read the age from the serial number

Every water heater has a rating plate, usually a sticker on the side of the tank near the controls. It lists the model number, the serial number, the capacity and the input rating. Most manufacturers hide the manufacture date in the serial number. A few of the common patterns:

If the sticker is gone or unreadable, a plumber can usually date a heater within a couple of years from its design, the venting style and the gas valve model. Federal efficiency rules changed in 2015, so a heater with a much taller, wider jacket than the old one it replaced is probably newer than that.

What actually wears a tank out

Water heater tanks are steel lined with a thin coat of glass. The glass is never perfect: tiny gaps exist from the factory and more open up as the tank heats and cools thousands of times. Wherever the steel is exposed, water would rust it, except for the anode rod. The anode is a rod of magnesium or aluminum that corrodes first, sacrificing itself to protect the exposed steel.

When the anode is used up, corrosion moves to the tank. The first sign is often rusty hot water, then a weep from the bottom seam a few months or years later. That is why the single most effective thing you can do for tank life is check the anode around year four or five and replace it when it is down to its core wire.

Heat stress is the second factor. Every time a gas burner fires under a layer of sediment, the tank bottom gets hotter than it should, and the glass lining cracks a little more. Flushing keeps that layer thin. See noisy water heaters and flushing for how it is done.

Pressure is the third. Street pressure above 80 psi, or a closed system with no expansion tank, flexes the tank with every heating cycle. A leaking relief valve is often the first clue.

Signs a water heater is near the end

• Rusty or brown hot water while cold water stays clear.
• Rumbling and popping that keeps coming back after a flush.
• Moisture around the base that is not coming from a fitting or valve.
• Hot water running out sooner than it used to, with no failed element to blame.
• Corrosion at the fittings on top of the tank, especially green or white crust.
• Age past the typical range for its type, even if it seems fine.

Any one of these on a tank under eight years is worth a repair visit. Two or more on an older tank mean it is time to plan a replacement on your schedule rather than waiting for a failure on a holiday weekend.

How to make a water heater last longer

1. Flush the tank yearly in hard-water areas, every two or three years in soft-water areas.
2. Replace the anode rod when it is mostly gone, usually around year four to six.
3. Keep pressure in check. A pressure reducing valve if street pressure is high, and an expansion tank on closed systems.
4. Set the temperature around 120°F. Hotter water speeds up both scale and corrosion.
5. Descale tankless units every year or as the manufacturer recommends for your hardness.
6. Keep the area clean around gas heaters so the air intake does not clog with lint and dust.

Most of these cost less than a single service call per year, and together they can stretch a tank's life by several years. Over a 30-year span in one house, that can mean buying two heaters instead of three.

Lifespan by where you live

Local conditions move the average a lot. Heaters in the desert Southwest, much of Texas, Florida and the Plains tend to sit at the short end of the range because of very hard water. Heaters in the Pacific Northwest, New England and the Southeast Piedmont, where the water is soft, often outlast the warranty by years if the anode is looked after.

Climate matters too. Heaters in unheated garages in cold climates work harder through the winter, because incoming water can be 30 or more degrees colder than in summer. Heaters in hot attics in the South run in extreme heat, which is hard on gas valves and electronic controls. Every city page on this site notes local water hardness and incoming water temperature for that reason.

Installation quality is the last big variable. Undersized venting, a missing expansion tank, no drain pan, or a gas tank in a closet with too little combustion air all shorten life, and they are all things a careful installer gets right the first time.

Does a warranty tell you anything?

Tank warranties of six, nine or twelve years mostly reflect a bigger anode rod, a thicker lining or more of both. The same brand often sells the same tank with different anodes under different warranty terms. A longer warranty is a reasonable signal of a longer-lived tank, though maintenance matters more than the sticker.

Warranties usually cover the tank against leaks and sometimes parts, but rarely labor. Keep the receipt and register the heater, because many manufacturers ask for proof of install date. Your plumber's own labor warranty is separate, so ask about it before the install.

Questions people ask