How Long Do Water Heaters Last?

The numbers, side by side

Different publishers quote slightly different ranges. They're close enough to plan around.

None of these sources gives gas and electric tanks separate lifespans. The tank is what wears out, and the tank is the same steel-and-glass-lining design either way. The difference is in the repairs along the way: an electric heater's elements and thermostats are cheap to replace, while a gas heater's burner, flue and gas valve need more attention.

Why tanks wear out

A tank heater dies from the inside. Water slowly attacks the steel wherever the glass lining has a flaw. A sacrificial anode rod corrodes in its place, which is why HomeGuide says plumbers recommend replacing the anode every 3 to 5 years. Once the anode is used up, the tank itself starts to rust, and eventually it leaks.

Sediment speeds that up. Minerals in the water settle at the bottom of the tank, insulate the water from the burner or lower element, and make the heater run longer and hotter. A.O. Smith links the rumbling and popping you hear from an old tank to sediment buildup.

A.O. Smith lists what moves a heater along its range: the location and design of the unit, the quality of installation, the maintenance schedule and water quality.

Hard water shortens the clock

Hard water is the biggest factor most owners can actually control. More dissolved minerals mean more sediment in a tank and more scale in a tankless heat exchanger. A.O. Smith says gas tankless heaters build up scale in the heat exchanger if the water isn't treated. If you don't know your hardness, our hard water page explains what the numbers mean and how to test.

A softener helps both types. It also eats anode rods faster, so check the anode more often if you have one.

How to tell how old yours is

Look at the nameplate on the side of the tank. It lists the model and serial numbers along with the capacity. Most manufacturers encode the build date in the serial number, but each brand uses its own format. Call the manufacturer or check its website with the serial in hand. Often the install date is also written on the tank or on a permit sticker nearby.

Signs it's near the end

• It's past 10 years old and leaking around the base, or running erratically.
• Water is pooling under the tank itself, not at a fitting. HomeGuide says a leak from the bottom of the tank usually means the tank is damaged.
• Discolored or smelly hot water, which A.O. Smith traces to hydrogen gas reacting with harmless bacteria.
• Noises that come back after a flush or a repair, which can mean a failing element or a cracked tank.

One of these alone isn't a death sentence. Rusty water can come from a dying anode rather than the tank. Two or three together on an older heater, though, and you should start pricing a replacement before it fails on its own schedule.

What makes a heater last longer

The maintenance list is short. A.O. Smith recommends:

1. Flush the tank at least once a year to clear sediment.
2. Test the relief valve by lifting its handle and letting it snap back.
3. Keep the thermostat at 120°F.
4. On gas models with air screens at the bottom, keep them clean.

Add an anode rod check to that list. A.O. Smith's troubleshooting guide says to inspect the anode every year or as needed. Our water heater maintenance checklist puts it all on one page.

Tankless owners have one job that matters more than everything else: descale on schedule, especially on hard water.

What to do next

If your heater is still short of the 8 to 12 year average and acting up, repair it. Start with water heater repair or the elements and thermostats guide for electric units.

If it's past 10 years, HomeGuide's rule is to consider replacing it, especially once a repair would cost more than half the price of a new one. Check water heater installation cost so you know what a fair quote looks like, and replace it on your timeline rather than after it floods the basement.