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How long do water heaters last? Signs it's time to replace yours

Water heaters don't come with an expiration date, but they do wear out, and a tank that fails usually fails by leaking. Knowing your heater's age and the warning signs lets you replace it on your schedule instead of after a flooded basement.

Safety first. If the tank itself is leaking, turn off its energy (breaker or gas control) and close the cold supply valve above it. If the temperature and pressure (T&P) relief valve is discharging hot water or steam, or you smell gas, stop and call a plumber (or your gas utility from outside the house for a gas smell).

Typical lifespan

Tank (storage) water heaters: manufacturers and plumbers commonly quote about 8 to 12 years for gas and electric tanks. Many last longer, some fail sooner.
Tankless water heaters: usually last considerably longer than tanks, often 20 years or more with regular descaling, because there's no tank to rust through. Parts like igniters, sensors and fans can still need replacing along the way.
Heat pump water heaters: are still tanks, so the tank itself ages much like a standard electric tank; the compressor and controls add parts that can need service.

The warranty length on the label (often 6, 9 or 12 years on tanks) is a rough hint at how the manufacturer built it, mainly the anode rod and tank lining, but it's not a guarantee of how long yours will last.

What shortens (or extends) a heater's life

Hard water and sediment. Minerals build up in the tank bottom or on elements, making the heater work harder and run hotter. Flushing per the manual helps.
The anode rod. This sacrificial metal rod corrodes so the steel tank doesn't. Once it's used up, the tank starts to rust from the inside. Checking it every few years, and replacing it when it's mostly eaten away, is one of the few things that can genuinely extend a tank's life.
High water pressure or no expansion tank. Pressure swings stress the tank and the relief valve. Many homes with a check valve or pressure-reducing valve need a thermal expansion tank.
Installation location. Heaters in hot attics, damp crawlspaces or garages exposed to freezing and moisture tend to have a harder life.

How to find your water heater's age

Look at the rating label on the side of the tank for the serial number. Most manufacturers encode the manufacture date in it, often as a letter for the month and digits for the year, or the year and week as the first four digits. The format varies by brand, so search "[brand] serial number date code" or call the manufacturer's support line with the serial number. If you can't read the label, an install date written on the tank or your home inspection report may help.

Signs it's time to replace

Water leaking from the tank itself (not a fitting or valve). A rusted-through tank can't be repaired; it needs replacement.
Rusty or brown hot water while the cold water is clear, especially from an older tank. This can mean the inside of the tank is corroding. (It can also be a spent anode rod or galvanized pipes, so it's worth confirming.)
Rust or corrosion on the tank, around the base, or at the inlet and outlet connections.
Loud rumbling or popping that flushing doesn't fix, usually from hardened sediment in an older tank.
Less hot water than it used to make, or water that's only lukewarm, after you've ruled out a thermostat, element or burner problem.
Frequent repairs on a heater that's already near or past the typical age range.

Repair or replace?

Many problems are worth repairing: a bad thermostat, heating element, thermocouple or flame sensor, gas control valve, drain valve, or relief valve. These are parts, not the tank. A good rule of thumb many plumbers use:

Repair if the heater is relatively young, the tank isn't leaking, and the fix is a replaceable part.
Replace if the tank itself is leaking or badly corroded, if it's near or past the typical lifespan and needs a significant repair, or if it can no longer keep up with your household.

Replacing before failure also gives you time to compare options, such as a different size, a high-efficiency or heat pump model, or tankless, rather than taking whatever is in stock on an emergency call.

Planning a replacement

Note the fuel type (gas, propane, electric), tank size in gallons, and the venting type from the existing label. Photos of the label and connections help when you get quotes.
Ask whether the quote includes a permit, haul-away of the old tank, a new expansion tank, earthquake straps where required, and bringing venting or gas lines up to current code.
Check for utility rebates or tax credits on efficient models before you buy.

Tip: Put a drain pan under the heater (piped to a drain if possible) and consider an inexpensive water leak alarm next to it. They won't stop a tank from failing, but they can turn a flood into a small puddle.